diagnostics: move text output member functions to correct file

diagnostics: move text output member functions to correct file

No functional change intended.

gcc/ChangeLog:
	* diagnostic-format-text.cc
	(diagnostic_text_output_format::after_diagnostic): Replace call to
	show_any_path with body, taken from diagnostic.cc.
	(diagnostic_text_output_format::build_prefix): Move here from
	diagnostic.cc, updating to use get_diagnostic_kind_text and
	diagnostic_get_color_for_kind.
	(diagnostic_text_output_format::file_name_as_prefix): Move here
	from diagnostic.cc
	(diagnostic_text_output_format::append_note): Likewise.
	* diagnostic-format-text.h
	(diagnostic_text_output_format::show_any_path): Drop decl.
	* diagnostic.cc
	(diagnostic_text_output_format::file_name_as_prefix): Move to
	diagnostic-format-text.cc.
	(diagnostic_text_output_format::build_prefix): Likewise.
	(diagnostic_text_output_format::show_any_path): Move to body of
	diagnostic_text_output_format::after_diagnostic.
	(diagnostic_text_output_format::append_note): Move to
	diagnostic-format-text.cc.

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