kv: Add established column to active_range_feeds table.

Add `established` column to `active_range_feeds` table.
This column is initialized to the time when the partial range feed
was established.  This allows us to determine, among other things,
whether or not the rangefeed is currently performing a catchup scan
(i.e. it's resolved column is 0), and how long the scan has been running
for.

Release Notes (enterprise): Add established time column
to `crdb_internal.active_range_feeds` virtual table to improve observability
and debugability of rangefeed system.

Release Justification: Low impact observability/debugability improvement.

pkg/kv/kvclient/kvcoord/dist_sender_rangefeed.go

@@ -124,6 +124,7 @@ type PartialRangeFeed struct {
 	StartTS           hlc.Timestamp
 	NodeID            roachpb.NodeID
 	RangeID           roachpb.RangeID
+	EstablishedTime   time.Time
 	LastValueReceived time.Time
 	Resolved          hlc.Timestamp
 }
@@ -262,8 +263,9 @@ func (ds *DistSender) partialRangeFeed(
 	// Register partial range feed with registry.
 	active := &activeRangeFeed{
 		PartialRangeFeed: PartialRangeFeed{
-			Span:    span,
-			StartTS: startFrom,
+			Span:            span,
+			StartTS:         startFrom,
+			EstablishedTime: timeutil.Now(),
 		},
 	}
 	rr.ranges.Store(active, nil)

pkg/sql/crdb_internal.go

@@ -5248,6 +5248,7 @@ CREATE TABLE crdb_internal.active_range_feeds (
   diff BOOL,
   node_id INT,
   range_id INT,
+  established INT,
   range_start STRING,
   range_end STRING,
   resolved STRING,
@@ -5270,6 +5271,7 @@ CREATE TABLE crdb_internal.active_range_feeds (
 					tree.MakeDBool(tree.DBool(rfCtx.WithDiff)),
 					tree.NewDInt(tree.DInt(rf.NodeID)),
 					tree.NewDInt(tree.DInt(rf.RangeID)),
+					tree.NewDInt(tree.DInt(rf.EstablishedTime.UTC().UnixNano())),
 					tree.NewDString(keys.PrettyPrint(nil /* valDirs */, rf.Span.Key)),
 					tree.NewDString(keys.PrettyPrint(nil /* valDirs */, rf.Span.EndKey)),
 					tree.NewDString(rf.Resolved.AsOfSystemTime()),

pkg/sql/logictest/testdata/logic_test/create_statements

@@ -39,6 +39,7 @@ CREATE TABLE crdb_internal.active_range_feeds (
    diff BOOL NULL,
    node_id INT8 NULL,
    range_id INT8 NULL,
+   established INT8 NULL,
    range_start STRING NULL,
    range_end STRING NULL,
    resolved STRING NULL,
@@ -50,6 +51,7 @@ CREATE TABLE crdb_internal.active_range_feeds (
    diff BOOL NULL,
    node_id INT8 NULL,
    range_id INT8 NULL,
+   established INT8 NULL,
    range_start STRING NULL,
    range_end STRING NULL,
    resolved STRING NULL,