fix: nimcheck improvements for generics, JS operators, Python 3.10+ syntax

- Add tolerantMode for generic Nim code with < > brackets
- Fix JS ?. and ?? operator tokenization
- Add Python 3.10 match/case keywords, underscore prefix support
- Fix f-string parsing operator precedence bug
- Fix duplicate foundClosing assignments in JS/PHP tokenizers
- Treat unknown flavors as info instead of error
- Add comprehensive test coverage for all fixes

tests/fixtures/python/valid.py

@@ -1,2 +1,11 @@
 def hello(name: str) -> str:
     return f"Hello, {name}!"
+
+def process(value):
+    match value:
+        case 1:
+            return 'one'
+        case _:
+            return 'other'
+
+_private_var = 42