libstdc++: Make testsuite usable with -fno-exceptions

libstdc++: Make testsuite usable with -fno-exceptions

Previously it was not possible to add -fno-exceptions to the testsuite
flags, because some files that are compiled by the v3-build_support
procedure failed with exceptions disabled.

This adjusts those files to still compile without exceptions (with
degraded functionality in some cases).

The sole testcase that explicitly checks for -fno-exceptions has also
been adjusted to use the more robust exceptions_enabled effective-target
keyword from gcc/testsuite/lib/target-supports.exp.

libstdc++-v3/ChangeLog:

	* testsuite/23_containers/vector/bool/72847.cc: Use the
	exceptions_enabled effective-target keyword instead of
	checking for an explicit -fno-exceptions option.
	* testsuite/util/testsuite_abi.cc (examine_symbol): Remove
	redundant try-catch.
	* testsuite/util/testsuite_allocator.h [!__cpp_exceptions]:
	Do not define check_allocate_max_size and memory_resource.
	* testsuite/util/testsuite_containers.h: Replace comment with
	#error if wrong standard dialect used.
	* testsuite/util/testsuite_shared.cc: Likewise.