Golang x/tools/gopls: add telemetry for refactor -> add and remove struct tags operations

Telemetry did not count any users that are using VSCode's modify struct tags command (https://screenshot.googleplex.com/5Y6R9KuXXv5Z55Q). Before we can fully remove it (as part of the effort to remove third-party dependencies from VSCode), we should also verify that people are using gopls' refactoring tools for adding and removing struct tags.