gh-98401: Invalid escape sequences emits SyntaxWarning (#99011)

A backslash-character pair that is not a valid escape sequence now
generates a SyntaxWarning, instead of DeprecationWarning.  For
example, re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d" is an
invalid escape sequence), use raw strings for regular expression:
re.compile(r"\d+\.\d+"). In a future Python version, SyntaxError will
eventually be raised, instead of SyntaxWarning.

Octal escapes with value larger than 0o377 (ex: "\477"), deprecated
in Python 3.11, now produce a SyntaxWarning, instead of
DeprecationWarning. In a future Python version they will be
eventually a SyntaxError.

codecs.escape_decode() and codecs.unicode_escape_decode() are left
unchanged: they still emit DeprecationWarning.

* The parser only emits SyntaxWarning for Python 3.12 (feature
  version), and still emits DeprecationWarning on older Python
  versions.
* Fix SyntaxWarning by using raw strings in Tools/c-analyzer/ and
  wasm_build.py.

Lib/test/test_codeop.py

@@ -310,8 +310,8 @@ def test_filename(self):
     def test_warning(self):
         # Test that the warning is only returned once.
         with warnings_helper.check_warnings(
-                (".*literal", SyntaxWarning),
-                (".*invalid", DeprecationWarning),
+                ('"is" with a literal', SyntaxWarning),
+                ("invalid escape sequence", SyntaxWarning),
                 ) as w:
             compile_command(r"'\e' is 0")
             self.assertEqual(len(w.warnings), 2)
@@ -321,9 +321,9 @@ def test_warning(self):
             warnings.simplefilter('error', SyntaxWarning)
             compile_command('1 is 1', symbol='exec')
 
-        # Check DeprecationWarning treated as an SyntaxError
+        # Check SyntaxWarning treated as an SyntaxError
         with warnings.catch_warnings(), self.assertRaises(SyntaxError):
-            warnings.simplefilter('error', DeprecationWarning)
+            warnings.simplefilter('error', SyntaxWarning)
             compile_command(r"'\e'", symbol='exec')
 
     def test_incomplete_warning(self):
@@ -337,7 +337,7 @@ def test_invalid_warning(self):
             warnings.simplefilter('always')
             self.assertInvalid("'\\e' 1")
         self.assertEqual(len(w), 1)
-        self.assertEqual(w[0].category, DeprecationWarning)
+        self.assertEqual(w[0].category, SyntaxWarning)
         self.assertRegex(str(w[0].message), 'invalid escape sequence')
         self.assertEqual(w[0].filename, '<input>')