(help-fns-function-name): New function

(help-fns-function-name): New function

Consolidate code used in profiler and help--describe-command,
and improve it while we're at it.
Also use #' to quote a few function names along the way.

* lisp/help-fns.el (help-fns--function-numbers, help-fns--function-names):
New vars.
(help-fns--display-function): New aux function.
(help-fns-function-name): New function, inspired from
`help--describe-command`.

* lisp/help.el (help--describe-command): Use `help-fns-function-name`.
(help--for-help-make-sections): Remove redundant "" arg to `mapconcat`.

* lisp/profiler.el (profiler-format-entry, profiler-fixup-entry):
Delete functions.
(profiler-report-make-entry-part): Use `help-fns-function-name` instead.
(profiler-report-find-entry): Use `push-button`.

* lisp/transient.el (transient--debug): Use `help-fns-function-name`
when available.