Add a bugreport command

This command should be something we can point issue reporters to for getting information that is useful for debugging problems. At the very least it should list the following things:

• extension version
• server version (and path if not downloaded by the extension)
• server config
• panics (and crashes of the proc-macro server) that happened since starting the server the last time including panic message and backtrace

Care must be taken to not include any potentially sensitive information in the common case and make it easily recognizable (and censorable) by the user when unavoidable (maybe some panic messages contain potentially sensitive information like project location).

It may also be nice to have a (by default disabled) option to include more sensitive information like the project repo and commit.

The issue names no files or tests. Start by locating how commands are registered and where extension, server configuration, and panic information are stored; then define the safe default output and the opt-in sensitive data boundary. Done means the command produces the requested diagnostic information while clearly exposing or censoring unavoidable sensitive values.