Simplify dir-watching strategy of w/didchangewatchedfiles

Simplify dir-watching strategy of w/didchangewatchedfiles

Instead of massaging the globPattern to match directories instead of
files, which is fragile, gather the list of directoris to watch by
matching the globPattern against every file recursively (except hidden
files and dirs).

This is still not 100% correct, but should do the right thing is most
cases.  Notably, if the correct dirs are being watched, the glob
pattern is matched against all existing and new files in those
directories, which does include hidden files.

* eglot.el (eglot-register-capability): match file globs against
files only.
(eglot--files-recursively): Rename from eglot--directories-recursively.

GitHub-reference: per https://github.com/joaotavora/eglot/issues/602