Eglot: better fix for bug#70724

Eglot: better fix for bug#70724

If the project's root is or destroyed , this may happen for a
variety of reasons, including reasons affecting non-reconnection
scenarios, so better to check in eglot--connect.

An Eglot "reconnection" has always created as accurate a copy of
the previous server object as possible, down to the 'eq'ness or
the saved initargs, language ids, etc.  So re-querying for
projects is not the thing to do here.

A new different server can be created with `M-x eglot` which will
ask about shutting down the existing one.

* lisp/progmodes/eglot.el (eglot-reconnect):  Revert previous change.
(eglot--connect):  Do sanity check here

(cherry picked from commit 6906ed28f1b4ac0cf0a2a725e7402290f33c26e2)