Avoid blinking for Eldoc's eldoc-documentation-eager strategy
"Blinking", or the very short-lived display of a lower priority Eldoc message, could happen if one of the members of eldoc-documentation-functions returned such elements shortly before returning a higher priority one. This can happen in the LSP engine Eglot for some LSP servers. Reported by Andrii Kolomoiets <andreyk.mad@gmail.com> and Dmitry Gutov <dgutov@yandex.ru>. * lisp/emacs-lisp/eldoc.el (eldoc--enthusiasm-curbing-timer): New variable. (eldoc-print-current-symbol-info): Use it. Use some more cl-isms.