PY-23452: fix sys.path for runners to make same as with real runners

* Python adds script folder as sys.path[0]. Since we run helper "helpers" dir is sys.path[0]. Pop it, and testrunner will patch sys.path as it is done with command line.
* Unittest is launched as module and it adds current dir -- pycharm mimics this behaviour.

python/testData/testRunner/env/unit/sysPath/test_sample.py

@@ -0,0 +1,10 @@
+import unittest
+import sys
+
+print("path[0]={0}".format(sys.path[0]))
+
+
+class SampleTest(unittest.TestCase):
+    def test_true(self):
+        self.assertTrue(True)
+