Change Attributes.Key debug strings to reference the API of the key

Users appear to be doing `attributes.toString()` to find keys they are
interested in and then unable to find the name of the Key in our API.
They workaround the problem by scanning through `attributes.keys()`
looking for the key of interest. This is an abuse of the keys() API and
unnecessary user friction. They'd happily use the API if they just knew
where to find it.

I added internal to some strings to make it clear that you shouldn't go
looking to use it. There were many strings I didn't change. I focused on
keys most likely to be seen by users, which meant keys in grpc-api and
keys that are available via transport attributes.

See grpc#1764 (comment)

alts/src/main/java/io/grpc/alts/internal/AltsProtocolNegotiator.java

@@ -58,10 +58,11 @@ public final class AltsProtocolNegotiator {
   private static final AsyncSemaphore handshakeSemaphore = new AsyncSemaphore(32);
 
   @Grpc.TransportAttr
-  public static final Attributes.Key<TsiPeer> TSI_PEER_KEY = Attributes.Key.create("TSI_PEER");
+  public static final Attributes.Key<TsiPeer> TSI_PEER_KEY =
+      Attributes.Key.create("internal:TSI_PEER");
   @Grpc.TransportAttr
   public static final Attributes.Key<Object> AUTH_CONTEXT_KEY =
-      Attributes.Key.create("AUTH_CONTEXT_KEY");
+      Attributes.Key.create("internal:AUTH_CONTEXT_KEY");
 
   private static final AsciiString SCHEME = AsciiString.of("https");
 

api/src/main/java/io/grpc/EquivalentAddressGroup.java

@@ -44,7 +44,7 @@ public final class EquivalentAddressGroup {
   @Attr
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/6138")
   public static final Attributes.Key<String> ATTR_AUTHORITY_OVERRIDE =
-      Attributes.Key.create("io.grpc.EquivalentAddressGroup.authorityOverride");
+      Attributes.Key.create("io.grpc.EquivalentAddressGroup.ATTR_AUTHORITY_OVERRIDE");
   private final List<SocketAddress> addrs;
   private final Attributes attrs;
 

api/src/main/java/io/grpc/Grpc.java

@@ -38,23 +38,23 @@ private Grpc() {
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1710")
   @TransportAttr
   public static final Attributes.Key<SocketAddress> TRANSPORT_ATTR_REMOTE_ADDR =
-      Attributes.Key.create("remote-addr");
+      Attributes.Key.create("io.grpc.Grpc.TRANSPORT_ATTR_REMOTE_ADDR");
 
   /**
    * Attribute key for the local address of a transport.
    */
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1710")
   @TransportAttr
   public static final Attributes.Key<SocketAddress> TRANSPORT_ATTR_LOCAL_ADDR =
-      Attributes.Key.create("local-addr");
+      Attributes.Key.create("io.grpc.Grpc.TRANSPORT_ATTR_LOCAL_ADDR");
 
   /**
    * Attribute key for SSL session of a transport.
    */
   @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1710")
   @TransportAttr
   public static final Attributes.Key<SSLSession> TRANSPORT_ATTR_SSL_SESSION =
-      Attributes.Key.create("ssl-session");
+      Attributes.Key.create("io.grpc.Grpc.TRANSPORT_ATTR_SSL_SESSION");
 
   /**
    * Annotation for transport attributes. It follows the annotation semantics defined

api/src/main/java/io/grpc/InternalConfigSelector.java

@@ -32,7 +32,7 @@
 public abstract class InternalConfigSelector {
   @NameResolver.ResolutionResultAttr
   public static final Attributes.Key<io.grpc.InternalConfigSelector> KEY
-      = Attributes.Key.create("io.grpc.config-selector");
+      = Attributes.Key.create("internal:io.grpc.config-selector");
 
   // Use PickSubchannelArgs for SelectConfigArgs for now. May change over time.
   /** Selects the config for an PRC. */

api/src/main/java/io/grpc/LoadBalancer.java

@@ -114,7 +114,7 @@ public abstract class LoadBalancer {
   @Internal
   @NameResolver.ResolutionResultAttr
   public static final Attributes.Key<Map<String, ?>> ATTR_HEALTH_CHECKING_CONFIG =
-      Attributes.Key.create("health-checking-config");
+      Attributes.Key.create("internal:health-checking-config");
   private int recursionCount;
 
   /**

binder/src/main/java/io/grpc/binder/internal/BinderTransport.java

@@ -109,17 +109,18 @@ public abstract class BinderTransport
    * active transport.
    */
   @Internal
-  public static final Attributes.Key<Integer> REMOTE_UID = Attributes.Key.create("remote-uid");
+  public static final Attributes.Key<Integer> REMOTE_UID =
+      Attributes.Key.create("internal:remote-uid");
 
   /** The authority of the server. */
   @Internal
   public static final Attributes.Key<String> SERVER_AUTHORITY =
-      Attributes.Key.create("server-authority");
+      Attributes.Key.create("internal:server-authority");
 
   /** A transport attribute to hold the {@link InboundParcelablePolicy}. */
   @Internal
   public static final Attributes.Key<InboundParcelablePolicy> INBOUND_PARCELABLE_POLICY =
-      Attributes.Key.create("inbound-parcelable-policy");
+      Attributes.Key.create("internal:inbound-parcelable-policy");
 
   /**
    * Version code for this wire format.

binder/src/main/java/io/grpc/binder/internal/BinderTransportSecurity.java

@@ -40,7 +40,7 @@
 public final class BinderTransportSecurity {
 
   private static final Attributes.Key<TransportAuthorizationState> TRANSPORT_AUTHORIZATION_STATE =
-      Attributes.Key.create("transport-authorization-state");
+      Attributes.Key.create("internal:transport-authorization-state");
 
   private BinderTransportSecurity() {}
 

grpclb/src/main/java/io/grpc/grpclb/GrpclbConstants.java

@@ -46,23 +46,23 @@ public final class GrpclbConstants {
    * Attribute key for gRPC LB server addresses.
    */
   public static final Attributes.Key<List<EquivalentAddressGroup>> ATTR_LB_ADDRS =
-      Attributes.Key.create("io.grpc.grpclb.lbAddrs");
+      Attributes.Key.create("io.grpc.grpclb.GrpclbConstants.ATTR_LB_ADDRS");
 
   /**
    * The naming authority of a gRPC LB server address.  It is an address-group-level attribute,
    * present when the address group is a LoadBalancer.
    */
   @EquivalentAddressGroup.Attr
   public static final Attributes.Key<String> ATTR_LB_ADDR_AUTHORITY =
-      Attributes.Key.create("io.grpc.grpclb.lbAddrAuthority");
+      Attributes.Key.create("io.grpc.grpclb.GrpclbConstants.ATTR_LB_ADDR_AUTHORITY");
 
   /**
    * Whether this EquivalentAddressGroup was provided by a GRPCLB server. It would be rare for this
    * value to be {@code false}; generally it would be better to not have the key present at all.
    */
   @EquivalentAddressGroup.Attr
   public static final Attributes.Key<Boolean> ATTR_LB_PROVIDED_BACKEND =
-      Attributes.Key.create("io.grpc.grpclb.lbProvidedBackend");
+      Attributes.Key.create("io.grpc.grpclb.GrpclbConstants.ATTR_LB_PROVIDED_BACKEND");
 
   private GrpclbConstants() { }
 }