c++: Revert dependent-array changes [PR 98116]

c++: Revert dependent-array changes [PR 98116]

The changes reverted here are exposing an existing problem with alias
template comparisons.  The typename_type changes are also incomplete,
possibly for similar reasons.  It seems safer to revert them, fix the
underlying issue and then move forwards.

The testcases is adjusted to more robustly check the specialization
table, and ICEs with and without the c++ changes.

Revert:
62fb1b9e0da c++: Fix array type dependency [PR 98107]
07589ca2b2c c++: typename_type structural comparison
29ae1d7751 c++: Extend build_array_type API

	PR c++/98116
	gcc/cp/
	* cp-tree.h (comparing_typenames): Delete.
	(cplus_build_array_type): Remove default parm.
	* pt.c (comparing_typenames): Delete.
	(spec_hasher::equal): Don't increment it.
	* tree.c (set_array_type_canon): Remove dep parm.
	(build_cplus_array_type): Remove dep parm changes.
	(cp_build_qualified_type_real): Remove dependent array type
	changes.
	(strip_typedefs): Likewise.
	* typeck.c (structural_comptypes): Revert comparing_typename
	changes.
	gcc/testsuite/
	* g++.dg/template/pr98116.C: Enable robust checking.