Simplify byte-code optimisation of pure functions

Simplify byte-code optimisation of pure functions

Most pure functions need no explicit optimisation; we can do away with
almost all uses of byte-optimize-predicate (now renamed to
byte-optimize-constant-args, since it is not just for predicates).
Also remove some superfluous arity warnings.

* lisp/emacs-lisp/byte-opt.el (byte-optimize-identity, byte-optimize-memq)
(byte-optimize-nth, byte-optimize-nthcdr):
Remove arity warnings and simplify.
* lisp/emacs-lisp/byte-opt.el (<, >, <=, >=, not, null, consp, listp)
(symbolp, stringp, string<, string-lessp, proper-list-p, logand)
(logior, logxor, lognot, car, cdr, car-safe, cdr-safe):
Remove superfluous byte-optimizer property.
(byte-optimize-predicate): Rename to byte-optimize-constant-args.
All uses changed.