BUG/MEDIUM: map/acl: pat_ref_{set,delete}_by_id regressions

BUG/MEDIUM: map/acl: pat_ref_{set,delete}_by_id regressions

Some regressions were introduced by 5fea59754b ("MEDIUM: map/acl:
Accelerate several functions using pat_ref_elt struct ->head list")

pat_ref_delete_by_id() fails to properly unlink and free the removed
reference because it bypasses the pat_ref_delete_by_ptr() made for
that purpose. This function is normally used everywhere the target
reference is set for removal, such as the pat_ref_delete() function
that matches pattern against a string. The call was probably skipped
by accident during the rewrite of the function.

With the above commit also comes another undesirable change:
both pat_ref_delete_by_id() and pat_ref_set_by_id() directly use the
<refelt> argument as a valid pointer (they do dereference it).

This is wrong, because <refelt> is unsafe and should be handled as an
ID, not a pointer (hence the function name). Indeed, the calling function
may directly pass user input from the CLI as <refelt> argument, so we must
first ensure that it points to a valid element before using it, else it is
probably invalid and we shouldn't touch it.

What this patch essentially does, is that it reverts pat_ref_set_by_id()
and pat_ref_delete_by_id() to pre 5fea59754b behavior. This seems like
it was the only optimization from the patch that doesn't apply.

Hopefully, after reviewing the changes with Fred, it seems that the 2
functions are only being involved in commands for manipulating maps or
acls on the cli, so the "missed" opportunity to improve their performance
shouldn't matter much. Nonetheless, if we wanted to speed up the reference
lookup by ID, we could consider adding an eb64 tree for that specific
purpose that contains all pattern references IDs (ie: pointers) so that
eb lookup functions may be used instead of linear list search.

The issue was raised by Marko Juraga as he failed to perform an an acl
removal by reference on the CLI on 2.9 which was known to work properly
on other versions.

It should be backported on 2.9.

Co-Authored-by: Frédéric Lécaille <flecaille@haproxy.com>