Eldoc: don't overdisplay if using eldoc-documentation-compose

Eldoc: don't overdisplay if using eldoc-documentation-compose

bug#62816

This is about a particular value for 'eldoc-documentation-strategy',
'eldoc-documentation-compose'.  Its helper
'eldoc--documentation-compose-1' was buggy.  It created the callback
for all the backends in 'eldoc-documentation-functions', but arranged
so that it could potentially be invoked immediately and trigger
display, half-defeating the purpose of the "patience" and causing
blinking in the echo area.

Now it creates all the callbacks beforehand and only then passes them
to the corresponding members of eldoc-documentation-functions.  This
sets up the correct state in eldoc--invoke-strategy.

* lisp/emacs-lisp/eldoc.el (eldoc--documentation-compose-1):
Delete.
(eldoc-documentation-compose)
(eldoc-documentation-compose-eagerly): Rework.