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

[madelinekalil]

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.

Note: we should not actually remove the VSCode command until we have implemented dialogue prompting in gopls, as this will allow users to specify the tag names to add and remove. Currently, the gopls codeactions can either add "json" tags or remove all struct tags, but this action cannot be customized.

[gopherbot]

Change https://go.dev/cl/688156 mentions this issue: gopls/internal/server: add counters for add and remove struct tags

[gopherbot]

Change https://go.dev/cl/688175 mentions this issue: internal/config: add counters for add and remove struct tags