shell: Fixed dns resolve and browse commands (#13451)

Currently the dns resolve and dns browse commands don't work,
as after adding ResolverProxy the shell Dns module uses wrong
Resolver instance and operations fail due to delegate set to null.

Utilized ResolverProxy instead of Resolve Instace().

src/lib/shell/commands/Dns.cpp

@@ -20,6 +20,7 @@
 #include <lib/core/PeerId.h>
 #include <lib/dnssd/Advertiser.h>
 #include <lib/dnssd/Resolver.h>
+#include <lib/dnssd/ResolverProxy.h>
 #include <lib/dnssd/platform/Dnssd.h>
 #include <lib/shell/Commands.h>
 #include <lib/shell/Engine.h>
@@ -113,6 +114,7 @@ class DnsShellResolverDelegate : public Dnssd::ResolverDelegate
 };
 
 DnsShellResolverDelegate sDnsShellResolverDelegate;
+Dnssd::ResolverProxy sResolverProxy;
 
 CHIP_ERROR ResolveHandler(int argc, char ** argv)
 {
@@ -124,7 +126,7 @@ CHIP_ERROR ResolveHandler(int argc, char ** argv)
     peerId.SetCompressedFabricId(strtoull(argv[0], NULL, 10));
     peerId.SetNodeId(strtoull(argv[1], NULL, 10));
 
-    return Dnssd::Resolver::Instance().ResolveNodeId(peerId, Inet::IPAddressType::kAny, Dnssd::Resolver::CacheBypass::On);
+    return sResolverProxy.ResolveNodeId(peerId, Inet::IPAddressType::kAny, Dnssd::Resolver::CacheBypass::On);
 }
 
 bool ParseSubType(int argc, char ** argv, Dnssd::DiscoveryFilter & filter)
@@ -184,7 +186,7 @@ CHIP_ERROR BrowseCommissionableHandler(int argc, char ** argv)
 
     streamer_printf(streamer_get(), "Browsing commissionable nodes...\r\n");
 
-    return Dnssd::Resolver::Instance().FindCommissionableNodes(filter);
+    return sResolverProxy.FindCommissionableNodes(filter);
 }
 
 CHIP_ERROR BrowseCommissionerHandler(int argc, char ** argv)
@@ -199,7 +201,7 @@ CHIP_ERROR BrowseCommissionerHandler(int argc, char ** argv)
 
     streamer_printf(streamer_get(), "Browsing commissioners...\r\n");
 
-    return Dnssd::Resolver::Instance().FindCommissioners(filter);
+    return sResolverProxy.FindCommissioners(filter);
 }
 
 CHIP_ERROR BrowseHandler(int argc, char ** argv)
@@ -221,8 +223,8 @@ CHIP_ERROR DnsHandler(int argc, char ** argv)
         return CHIP_NO_ERROR;
     }
 
-    Dnssd::Resolver::Instance().Init(DeviceLayer::UDPEndPointManager());
-    Dnssd::Resolver::Instance().SetResolverDelegate(&sDnsShellResolverDelegate);
+    sResolverProxy.Init(DeviceLayer::UDPEndPointManager());
+    sResolverProxy.SetResolverDelegate(&sDnsShellResolverDelegate);
 
     return sShellDnsSubcommands.ExecCommand(argc, argv);
 }