coroutines: Adjust outlined function names [PR95520].

coroutines: Adjust outlined function names [PR95520].

The mechanism used to date for uniquing the coroutine helper
functions (actor, destroy) was over-complicating things and
leading to the noted PR and also difficulties in setting
breakpoints on these functions (so this will help PR99215 as
well).

This implementation delegates the adjustment to the mangling
to write_encoding() which necessitates some book-keeping so
that it is possible to determine which of the coroutine
helper names is to be mangled.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
PR c++/95520 - [coroutines] __builtin_FUNCTION() returns mangled .actor instead of original function name

	PR c++/95520

gcc/cp/ChangeLog:

	* coroutines.cc (struct coroutine_info): Add fields for
	actor and destroy function decls.
	(to_ramp): New.
	(coro_get_ramp_function): New.
	(coro_get_actor_function): New.
	(coro_get_destroy_function): New.
	(act_des_fn): Set up mapping between ramp, actor and
	destroy functions.
	(morph_fn_to_coro): Adjust interface to the builder for
	helper function decls.
	* cp-tree.h (DECL_ACTOR_FN, DECL_DESTROY_FN, DECL_RAMP_FN,
	JOIN_STR): New.
	* mangle.c (write_encoding): Handle coroutine helpers.
	(write_unqualified_name): Handle lambda coroutine helpers.

gcc/testsuite/ChangeLog:

	* g++.dg/coroutines/pr95520.C: New test.

(cherry picked from commit 237ab3ee49e2f3110accfcc03b6c0df8b4889f15)