internal/lsp: return all code action kinds with context.only prefix

When context.Only is passed in the codeAction request, all code actions
that have a matching prefix should be returned. For example:

context.Only: "refactor"
want: "refactor.extract", "refactor.rewrite"

Fixes golang/go#49263

Change-Id: I4bcea4a0b0097f3187f3d7055cbb73b518008107
Reviewed-on: https://go-review.googlesource.com/c/tools/+/361834
Trust: Suzy Mueller <suzmue@golang.org>
Run-TryBot: Suzy Mueller <suzmue@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/lsp/code_action.go

@@ -51,7 +51,12 @@ func (s *Server) codeAction(ctx context.Context, params *protocol.CodeActionPara
 	} else {
 		wanted = make(map[protocol.CodeActionKind]bool)
 		for _, only := range params.Context.Only {
-			wanted[only] = supportedCodeActions[only] || explicit[only]
+			for k, v := range supportedCodeActions {
+				if only == k || strings.HasPrefix(string(k), string(only)+".") {
+					wanted[k] = wanted[k] || v
+				}
+			}
+			wanted[only] = wanted[only] || explicit[only]
 		}
 	}
 	if len(supportedCodeActions) == 0 {