Move all new's to global_arena, and remove ASAN disabling (#690)

Note this changes identifiers from char* to string to avoid malloc.

Fixes #580

executable_semantics/tests.py

@@ -111,9 +111,6 @@ def _update_list(use_git_state):
 
 def _update_golden(test):
     """Updates the golden file for `test` by running executable_semantics."""
-    # TODO(#580): Remove this when leaks are fixed.
-    env = os.environ.copy()
-    env["ASAN_OPTIONS"] = "detect_leaks=0"
     # Invoke the test update directly in order to allow parallel execution
     # (`bazel run` will serialize).
     p = subprocess.run(
@@ -123,7 +120,6 @@ def _update_golden(test):
             "%s/executable_semantics %s/%s.carbon" % (_BINDIR, _TESTDATA, test),
             "--update",
         ],
-        env=env,
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
     )