Add support for using Python 3.6 interpreters (#18454)

Applies a patch to use Python 3.6 compatible types in our vendored
`packaging` implementation used in the interpreter query script. Adds
Python 3.6 and 3.7 test coverage in CI.

crates/uv-python/python/get_interpreter_info.py

@@ -444,7 +444,7 @@ def get_operating_system_and_architecture():
         version = None
         architecture = version_arch
 
-    if sys.version_info < (3, 7):
+    if sys.version_info < (3, 6):
         print(
             json.dumps(
                 {