tests: check min required python version with vermin (#14289)

This commit removes the `python_version.py` unit test module
and the vendored dependencies `pyqver2.py` and `pyqver3.py`.
It substitutes them with an equivalent check done using
`vermin` that is run as a separate workflow via Github Actions.

This allows us to delete 2 vendored dependencies that are unmaintained
and substitutes them with a maintained tool.

Also, updates the list of vendored dependencies.

lib/spack/llnl/util/cpu/microarchitecture.py

@@ -8,7 +8,7 @@
 import warnings
 
 try:
-    from collections.abc import Sequence
+    from collections.abc import Sequence  # novm
 except ImportError:
     from collections import Sequence
 

lib/spack/llnl/util/cpu/schema.py

@@ -6,7 +6,7 @@
 import os.path
 
 try:
-    from collections.abc import MutableMapping
+    from collections.abc import MutableMapping  # novm
 except ImportError:
     from collections import MutableMapping
 

lib/spack/llnl/util/lang.py

@@ -612,12 +612,14 @@ def load_module_from_file(module_name, module_path):
     """
     if sys.version_info[0] == 3 and sys.version_info[1] >= 5:
         import importlib.util
-        spec = importlib.util.spec_from_file_location(module_name, module_path)
-        module = importlib.util.module_from_spec(spec)
+        spec = importlib.util.spec_from_file_location(  # novm
+            module_name, module_path)
+        module = importlib.util.module_from_spec(spec)  # novm
         spec.loader.exec_module(module)
     elif sys.version_info[0] == 3 and sys.version_info[1] < 5:
         import importlib.machinery
-        loader = importlib.machinery.SourceFileLoader(module_name, module_path)
+        loader = importlib.machinery.SourceFileLoader(  # novm
+            module_name, module_path)
         module = loader.load_module()
     elif sys.version_info[0] == 2:
         import imp