test: add new python linter to check file names and permissions

Replaces the existing tests in the test/lint/lint-filenames.sh and test/lint/lint-shebang.sh linter tests, as well as adding some new and increased testing.
Summary of tests:
- Checks every file in the repository against an allowed regexp to make sure only lowercase or uppercase alphanumerics (a-zA-Z0-9), underscores (_), hyphens (-), at (@) and dots (.) are used in repository filenames.
- Checks only source files (*.cpp, *.h, *.py, *.sh) against a stricter allowed regexp to make sure only lowercase alphanumerics (a-z0-9), underscores (_), hyphens (-) and dots (.) are used in source code filenames. Additionally there is an exception regexp for directories or files which are excepted from matching this regexp (This should replicate the existing test/lint/lint-filenames.sh test)
- Checks all files in the repository match an allowed executable or non-executable file permission octal. Additionally checks that for executable files, the file contains a shebang line.
- Checks that for executable .py and .sh files, the shebang line used matches an allowable list of shebangs (This should replicate the existing test/lint/lint-shebang.sh test)
- Checks every file that contains a shebang line to ensure it has an executable permission

Fixes #21729

test/README.md

@@ -273,7 +273,7 @@ Please be aware that on Linux distributions all dependencies are usually availab
 Individual tests can be run by directly calling the test script, e.g.:
 
 ```
-test/lint/lint-filenames.sh
+test/lint/lint-files.sh
 ```
 
 You can run all the shell-based lint tests by running: