PR libstdc++/80276 fix template argument handling in type printers

PR libstdc++/80276 fix template argument handling in type printers

	PR libstdc++/80276
	* python/libstdcxx/v6/printers.py (strip_inline_namespaces): New.
	(get_template_arg_list): New.
	(StdVariantPrinter._template_args): Remove, use get_template_arg_list
	instead.
	(TemplateTypePrinter): Rewrite to work with gdb.Type objects instead
	of strings and regular expressions.
	(add_one_template_type_printer): Adapt to new TemplateTypePrinter.
	(FilteringTypePrinter): Add docstring. Match using startswith. Use
	strip_inline_namespaces instead of strip_versioned_namespace.
	(add_one_type_printer): Prepend namespace to match argument.
	(register_type_printers): Add type printers for char16_t and char32_t
	string types and for types using cxx11 ABI. Update calls to
	add_one_template_type_printer to provide default argument dicts.
	* testsuite/libstdc++-prettyprinters/80276.cc: New test.
	* testsuite/libstdc++-prettyprinters/whatis.cc: Remove tests for
	basic_string<unsigned char> and basic_string<signed char>.
	* testsuite/libstdc++-prettyprinters/whatis2.cc: Duplicate whatis.cc
	to test local variables, without overriding _GLIBCXX_USE_CXX11_ABI.

From-SVN: r256689