c++: Don't purge the satisfaction caches

c++: Don't purge the satisfaction caches

The adoption of P2104 ("Disallow changing concept values") means we can
memoize the result of satisfaction indefinitely and no longer have to
clear the satisfaction caches on various events that would affect
satisfaction.  To that end, this patch removes the invalidation routine
clear_satisfaction_cache and adjusts its callers appropriately.

This provides a large reduction in compile time and memory use in some
cases.  For example, on the libstdc++ test std/ranges/adaptor/join.cc,
compile time and memory usage drops nearly 75%, from 7.5s/770MB to
2s/230MB, with a --enable-checking=release compiler.

gcc/cp/ChangeLog:

	* class.c (finish_struct_1): Don't call clear_satisfaction_cache.
	* constexpr.c (clear_cv_and_fold_caches): Likewise.  Remove bool
	parameter.
	* constraint.cc (clear_satisfaction_cache): Remove definition.
	* cp-tree.h (clear_satisfaction_cache): Remove declaration.
	(clear_cv_and_fold_caches): Remove bool parameter.
	* typeck2.c (store_init_value): Remove argument to
	clear_cv_and_fold_caches.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-complete1.C: Delete test that became
	ill-formed after P2104.