Optimise assoc and rassoc with symbol key to assq and rassq

This is the same transformation made for member to memq.

* lisp/emacs-lisp/byte-opt.el (byte-optimize-assoc): New function.
(assoc, rassoc): Set the byte-optimizer property.
1 job for master in 31 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #6563
test-all

00:00:31

 
Name Stage Failure
failed
test-all Test
error: cannot lock ref 'refs/remotes/origin/master': Unable to create '/builds/emacs/emacs/.git/refs/remotes/origin/master.lock': File exists.

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.
fatal: failed to run reflog
ERROR: Job failed: exit code 1