diagnostics: output formats: use references for non-null pointers

diagnostics: output formats: use references for non-null pointers

No functional change intended.

gcc/ChangeLog:
	* diagnostic-format-json.cc (json_from_expanded_location): Make
	"static". Pass param "context" by reference, as it cannot be null.
	(json_from_location_range): Likewise for param "context".
	(json_from_fixit_hint): Likewise.
	(make_json_for_path): Likewise.
	(json_output_format::on_end_diagnostic): Update for above changes.
	(diagnostic_output_format_init_json::diagnostic_output_format_init_json):
	Pass param "context" by reference, as it cannot be null.
	(diagnostic_output_format_init_json_stderr): Likewise.
	(diagnostic_output_format_init_json_file): Likewise.
	(selftest::test_unknown_location): Update for above changes.
	(selftest::test_bad_endpoints): Likewise.
	* diagnostic-format-sarif.cc (sarif_builder::m_context): Convert
	from pointer to reference.
	(sarif_invocation::add_notification_for_ice): Convert both params
	from pointers to references.
	(sarif_invocation::prepare_to_flush): Likewise for "context".
	(sarif_result::on_nested_diagnostic): Likewise for "context" and
	"builder".
	(sarif_result::on_diagram): Likewise.
	(sarif_ice_notification::sarif_ice_notification): Likewise.
	(sarif_builder::sarif_builder): Likewise for "context".
	(sarif_builder::end_diagnostic): Likewise.
	(sarif_builder::emit_diagram): Likewise.
	(sarif_builder::make_result_object): Likewise.
	(make_reporting_descriptor_object_for_warning): Likewise.
	(sarif_builder::make_locations_arr): Update for change to m_context.
	(sarif_builder::get_sarif_column): Likewise.
	(sarif_builder::make_message_object_for_diagram): Convert "context"
	from pointer to reference.
	(sarif_builder::make_tool_object): Likewise for "m_context".
	(sarif_builder::make_driver_tool_component_object): Likewise.
	(sarif_builder::get_or_create_artifact): Likewise.
	(sarif_builder::maybe_make_artifact_content_object): Likewise.
	(sarif_builder::get_source_lines): Likewise.
	(sarif_output_format::on_end_diagnostic): Update for above changes.
	(sarif_output_format::on_diagram): Likewise.
	(sarif_output_format::sarif_output_format): Likewise.
	(diagnostic_output_format_init_sarif): Convert param "context"
	from pointer to reference.
	(diagnostic_output_format_init_sarif_stderr): Likewise.
	(diagnostic_output_format_init_sarif_file): Likewise.
	(diagnostic_output_format_init_sarif_stream): Likewise.
	* diagnostic.cc (diagnostic_output_format_init): Likewise.
	* diagnostic.h (diagnostic_output_format_init): Likewise.
	(diagnostic_output_format_init_json_stderr): Likewise.
	(diagnostic_output_format_init_json_file): Likewise.
	(diagnostic_output_format_init_sarif_stderr): Likewise.
	(diagnostic_output_format_init_sarif_file): Likewise.
	(diagnostic_output_format_init_sarif_stream): Likewise.
	(json_from_expanded_location): Delete decl.
	* gcc.cc (driver_handle_option): Update for change to
	diagnostic_output_format_init.
	* opts.cc (common_handle_option): Likewise.

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