json: implement JSON pointer; use it in sarif-replay [PR117988]

json: implement JSON pointer; use it in sarif-replay [PR117988]

This patch extends our json class to track JSON pointers (RFC 6901),
and then uses this within sarif-replay to provide logical locations
within the JSON when reporting on issues in the SARIF.

gcc/ChangeLog:
	PR sarif-replay/117988
	* json.cc (json::pointer::token::token): New ctors.
	(json::pointer::token::~token): New.
	(json::pointer::token::operator=): New.
	(json::object::set): Set the value's m_pointer_token.
	(json::array::append): Likewise.
	* json.h (json::pointer::token): New struct.
	(json::value::get_pointer_token): New accessor.
	(json::value::m_pointer_token): New field.
	* libsarifreplay.cc (get_logical_location_kind_for_json_kind):
	New.
	(make_logical_location_from_jv): New.
	(sarif_replayer::report_problem): Set the logical location of the
	diagnostic.

gcc/testsuite/ChangeLog:
	PR sarif-replay/117988
	* sarif-replay.dg/2.1.0-invalid/3.1-not-an-object.sarif: Add
	expected logical location.
	* sarif-replay.dg/2.1.0-invalid/3.11.11-missing-arguments-for-placeholders.sarif:
	Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.11.11-not-enough-arguments-for-placeholders.sarif:
	Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.11.5-unescaped-braces.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.13.2-no-version.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.13.2-version-not-a-string.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.13.4-bad-runs.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.13.4-no-runs.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.13.4-non-object-in-runs.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.27.10-bad-level.sarif: Likewise.
	* sarif-replay.dg/2.1.0-invalid/3.33.3-index-out-of-range.sarif: Likewise.
	* sarif-replay.dg/2.1.0-unhandled/3.27.10-none-level.sarif: Likewise.

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