libgdiagnostics: consolidate logical locations

libgdiagnostics: consolidate logical locations

This patch updates diagnostic_manager_new_logical_location so
that repeated calls with the same input values yield the same
instance of diagnostic_logical_location.

Doing so allows the path-printing logic to properly consolidate runs of
events, whereas previously it could treat each event as having a
distinct logical location, and thus require them to be printed
separately; this greatly improves the output of sarif-replay when
displaying execution paths.

gcc/ChangeLog:
	* doc/libgdiagnostics/topics/logical-locations.rst
	(diagnostic_manager_new_logical_location): Add note about repeated
	calls.
	* libgdiagnostics.cc: Define INCLUDE_MAP.
	(class owned_nullable_string): Add copy ctor and move ctor.
	(owned_nullable_string::operator<): New.
	(diagnostic_logical_location::operator<): New.
	(diagnostic_manager::new_logical_location): Use m_logical_locs to
	"uniquify" instances, converting it to a std::map.
	(diagnostic_manager::logical_locs_map_t): New typedef.
	(diagnostic_manager::t m_logical_locs): Convert from a std::vector
	to a std::map.
	(diagnostic_execution_path::same_function_p): Update comment.

gcc/testsuite/ChangeLog:
	* libgdiagnostics.dg/test-logical-location.c: Include <assert.h>.
	Verify that creating a diagnostic_logical_location with equal
	values yields the same instance.
	* sarif-replay.dg/2.1.0-valid/malloc-vs-local-4.c.sarif: New test.
	* sarif-replay.dg/2.1.0-valid/signal-1.c.moved.sarif: Update
	expected output to show logical location and for consolidation of
	events into runs.
	* sarif-replay.dg/2.1.0-valid/signal-1.c.sarif: Likewise.
	* sarif-replay.dg/2.1.0-valid/spec-example-4.sarif: Likewise.

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