Add 'system python' validation for some py scripts.

The goal of this test is to try to import some critical py scripts with the
system python of the building machine.
The main target is to ensure that these py scripts remain usable by all
buildbot machines, as some of them are using fairly outdated python
versions.

Current status:
* Scripts in `build_files` and `docs` are checked.
* Some python scripts in `build_files` were 'reverted' to be compatible
  with older required python version currently (3.6).
* A few scripts are excluded from the test, mostly because they use Blender's
  `bpy` module, which means they are only intended to be ran with Blender's
  python anyway.
* The test is only enabled for Linux buildbots currently, as they use the
  oldest Python by far.

Notes:
* Some more scripts are likely to be moved around in the future.
* Whether these tests need to be enabled on windows or macos platforms remains
  an open question.

Pull Request: https://projects.blender.org/blender/blender/pulls/130746

doc/manpage/blender.1.py

@@ -20,6 +20,7 @@ import time
 
 from typing import (
     TextIO,
+    Dict,
 )
 
 
@@ -31,7 +32,7 @@ def man_format(data: str) -> str:
     return data
 
 
-def blender_extract_info(blender_bin: str) -> dict[str, str]:
+def blender_extract_info(blender_bin: str) -> Dict[str, str]:
     blender_env = {
         "ASAN_OPTIONS": (
             os.environ.get("ASAN_OPTIONS", "") +