gopls/internal/test/integration: slightly more ergonomic FolderSettings

After setting CL 563475 for autosubmit, I realized we should use a
slightly more ergonomic pattern for configuring folder settings.

Change-Id: I3a4e9e3dca3f4865c3bca02258cd81ff2b7024b3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/563402
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Findley <rfindley@google.com>

gopls/internal/test/integration/misc/configuration_test.go

@@ -78,13 +78,13 @@ type B struct {
 
 	WithOptions(
 		WorkspaceFolders("a"),
-		FolderSettings(map[string]Settings{
+		FolderSettings{
 			"a": {
 				"analyses": map[string]bool{
 					"composites": false,
 				},
 			},
-		}),
+		},
 	).Run(t, files, func(t *testing.T, env *Env) {
 		env.OpenFile("a/a.go")
 		env.AfterChange(NoDiagnostics())

gopls/internal/test/integration/options.go

@@ -115,16 +115,16 @@ func WorkspaceFolders(relFolders ...string) RunOption {
 //
 // Use in conjunction with WorkspaceFolders to have different settings for
 // different folders.
-func FolderSettings(folderSettings map[string]Settings) RunOption {
+type FolderSettings map[string]Settings
+
+func (fs FolderSettings) set(opts *runConfig) {
 	// Re-use the Settings type, for symmetry, but translate back into maps for
 	// the editor config.
 	folders := make(map[string]map[string]any)
-	for k, v := range folderSettings {
+	for k, v := range fs {
 		folders[k] = v
 	}
-	return optionSetter(func(opts *runConfig) {
-		opts.editor.FolderSettings = folders
-	})
+	opts.editor.FolderSettings = folders
 }
 
 // EnvVars sets environment variables for the LSP session. When applying these