testsuite: use check-jsonschema for validating .sarif files [PR109360]

As reported here:
  https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655434.html


the schema validation I added for generated .sarif files in
r15-1541-ga84fe222029ff2 used the "jsonschema" command line tool, which
has been deprecated by more recent versions of the Python 3 "jsonschema"
module.

This patch updates the validation to use the more recent
"check-jsonschema" command line tool, from the Python 3 "check-jsonschema"
module, fixing the testsuite FAILs due to the deprecation message.

As an added bonus, the output on validation failures is *much* nicer, e.g.
if I undo r15-1540-g9f4fdc3acebcf6, the error messages begin like this:
verify-sarif-file: res: Schema validation errors were encountered.
  diagnostic-format-sarif-file-bad-utf8-pr109098-1.c.sarif::$.runs[0].results[0].locations[0].physicalLocation.region.startColumn: 0 is less than the minimum of 1
  diagnostic-format-sarif-file-bad-utf8-pr109098-1.c.sarif::$.runs[0].results[0].relatedLocations[0].physicalLocation.region.startColumn: 0 is less than the minimum of 1
  diagnostic-format-sarif-file-bad-utf8-pr109098-1.c.sarif::$.runs[0].results[0].relatedLocations[1].physicalLocation.region.startColumn: 0 is less than the minimum of 1
  diagnostic-format-sarif-file-bad-utf8-pr109098-1.c.sarif::$.runs[0].results[0].relatedLocations[2].physicalLocation.region.startColumn: 0 is less than the minimum of 1
child process exited abnormally
FAIL: c-c++-common/diagnostic-format-sarif-file-bad-utf8-pr109098-1.c  -Wc++-compat   (test .sarif output against SARIF schema)

Tested with Python 3.8 with check_jsonschema 0.28.6

gcc/ChangeLog:
	PR testsuite/109360
	* doc/install.texi (Python3 modules): Update SARIF validation
	requirement to use check-jsonschema rather than jsonschema.

gcc/testsuite/ChangeLog:
	PR testsuite/109360
	* lib/scansarif.exp (verify-sarif-file): Use check-jsonschema
	rather than jsonschema, updating the invocation accordingly.
	* lib/target-supports.exp (check_effective_target_jsonschema): Convert
	to...
	(check_effective_target_check_jsonschema): ...this.

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