Again speed up directory watching

Again speed up directory watching

Previously, given a number of globs, Eglot would try to place system
watchers only in those subdirectories that could potentially be
matched by a glob.  This meant traversing the whole tree, which could
be impractical.  Just place watchers in every subdirectory of the
project (you may run out of watchers).

* eglot.el (eglot-register-capability): Simplify.
(eglot--files-recursively): Delete.
(eglot--directories-recursively): Fix.

GitHub-reference: fix https://github.com/joaotavora/eglot/issues/697
GitHub-reference: fix https://github.com/joaotavora/eglot/issues/645