twister: Add "path" entry to json test report

"Path" is a path (relative to zephyr) to a directory with test suite's
definition. Such entry helps to locate a given test.

Signed-off-by: Maciej Perkowski <Maciej.Perkowski@nordicsemi.no>

scripts/pylib/twister/twisterlib/reports.py

@@ -258,6 +258,7 @@ class Reporting:
                 "name": instance.testsuite.name,
                 "arch": instance.platform.arch,
                 "platform": instance.platform.name,
+                "path": instance.testsuite.source_dir_rel
             }
             if instance.run_id:
                 suite['run_id'] = instance.run_id

scripts/pylib/twister/twisterlib/testsuite.py

@@ -395,6 +395,8 @@ class TestSuite(DisablePyTestCollectionMixin):
         self.id = name
 
         self.source_dir = suite_path
+        self.source_dir_rel = os.path.relpath(os.path.realpath(suite_path),
+                                              start=canonical_zephyr_base)
         self.yamlfile = suite_path
         self.testcases = []