diagnostics: use unicode art for interprocedural depth

diagnostics: use unicode art for interprocedural depth

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/out-of-bounds-diagram-1-emoji.c: Update expected
	output to use unicode for depth indication.
	* gcc.dg/analyzer/out-of-bounds-diagram-1-unicode.c: Likewise.

gcc/ChangeLog:
	* text-art/theme.cc (ascii_theme::get_cppchar): Add
	cell_kind::INTERPROCEDURAL_*.
	(unicode_theme::get_cppchar): Likewise.
	* text-art/theme.h (theme::cell_kind): Likewise.
	* tree-diagnostic-path.cc:
	(thread_event_printer::print_swimlane_for_event_range): Use the
	above to get characters for indicating interprocedural stack
	depth activity, falling back to ascii.
	(selftest::test_interprocedural_path_1): Test with both ascii
	and unicode themes.
	(selftest::test_interprocedural_path_2): Likewise.
	(selftest::test_recursion): Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>