testsuite: add hostedlib requirements to multiple C++ tests

testsuite: add hostedlib requirements to multiple C++ tests

Various C++ tests added in the gcc-15 cycle require features that are
only available when libstdc++-v3 is built in hosted mode, so they fail
when this is not the case.  Skip them if ! hostedlib.

for  gcc/testsuite/ChangeLog

	* g++.dg/DRs/dr2836.C: Skip if ! hostedlib.
	* g++.dg/alias-checks.C: Likewise.
	* g++.dg/contracts/pr116490.C: Likewise.
	* g++.dg/coroutines/torture/pr121219.C: Likewise.
	* g++.dg/cpp2a/constexpr-vector1.C: Likewise.
	* g++.dg/ext/is_virtual_base_of.C: Likewise.
	* g++.dg/modules/contracts-5_b.C: Likewise.
	* g++.dg/modules/gmf-xtreme.C: Likewise.
	* g++.dg/modules/lto-3_a.H: Likewise.
	* g++.dg/modules/lto-3_b.C: Likewise.
	* g++.dg/modules/xtreme-header-8.C: Likewise.
	* g++.dg/opt/pr119274.C: Likewise.
	* g++.dg/pr117222.C: Likewise.
	* g++.dg/torture/pr105769-1.C: Likewise.
	* g++.dg/torture/pr118521.C: Likewise.
	* g++.dg/tree-ssa/deque-1.C: Likewise.
	* g++.dg/tree-ssa/deque-2.C: Likewise.
	* g++.dg/tree-ssa/pr109442.C: Likewise.
	* g++.dg/tree-ssa/pr110819.C: Likewise.
	* g++.dg/tree-ssa/pr116868.C: Likewise.
	* g++.dg/tree-ssa/pr58483.C: Likewise.
	* g++.dg/tree-ssa/pr80331.C: Likewise.
	* g++.dg/tree-ssa/pr87502.C: Likewise.
	* g++.dg/tree-ssa/pr96945.C: Likewise.
	* g++.dg/tree-ssa/string-1.C: Likewise.