diagnostics: handle SGR codes in line_label::m_display_width

diagnostics: handle SGR codes in line_label::m_display_width

gcc/ChangeLog:
	* diagnostic-show-locus.cc: Define INCLUDE_VECTOR and include
	"text-art/types.h".
	(line_label::line_label): Drop "policy" argument.  Use
	styled_string::calc_canvas_width when computing m_display_width,
	as this skips SGR codes.
	(layout::print_any_labels): Update for line_label ctor change.
	(selftest::test_one_liner_labels_utf8): Update expected text to
	reflect that the labels can fit on one line if we don't get
	confused by SGR colorization codes.

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