Warn about suspicious interface usage at compile-time

Warn about suspicious interface usage at compile-time

For fun, set eglot-strict-mode to '(disallow-non-standard-keys
enforce-required-keys enforce-optional-keys) when compiling, or just
use flymake-mode in eglot.el.

* eglot.el (eglot--lsp-interface-alist): Use in compile-time.
Order alphabetically.  Fix a few bugs.
(eglot-strict-mode): Disallow non-standard-keys when compiling.
Update docstring.
(eglot--keywordize-vars, eglot--check-interface): New
compile-time-helpers.
(eglot--dbind, eglot--dcase): Use new helpers.