internal/mcp: add iterator methods resources and prompts

This CL streamlines the client side pagination logic by adding a generic
helper that handles pagination. This also simplifies the existing tools
iterator method.

Change-Id: If4304deda1ccd22d0c4580d76deaefc64e5dfeb9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/676975
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

mcp/generate.go

@@ -332,6 +332,13 @@ func writeDecl(configName string, config typeConfig, def *jsonschema.Schema, nam
 		fmt.Fprintf(w, "\nfunc (x *%s) GetMeta() *Meta { return &x.Meta }", typeName)
 	}
 
+	if _, ok := def.Properties["cursor"]; ok {
+		fmt.Fprintf(w, "\nfunc (x *%s) cursorPtr() *string { return &x.Cursor }", typeName)
+	}
+	if _, ok := def.Properties["nextCursor"]; ok {
+		fmt.Fprintf(w, "\nfunc (x *%s) nextCursorPtr() *string { return &x.NextCursor }", typeName)
+	}
+
 	return nil
 }