Deprecate the snow.Context.Lock (#3762)

Author: StephenButtolph

snow/context.go

@@ -42,7 +42,12 @@ type Context struct {
 	CChainID    ids.ID
 	AVAXAssetID ids.ID
 
-	Log          logging.Logger
+	Log logging.Logger
+	// Deprecated: This lock should not be used unless absolutely necessary.
+	// This lock will be removed in a future release once it is replaced with
+	// more granular locks.
+	//
+	// Warning: This lock is not correctly implemented over the rpcchainvm.
 	Lock         sync.RWMutex
 	SharedMemory atomic.SharedMemory
 	BCLookup     ids.AliaserReader