Support regex matching when parsing CI configuration file

[jo-basevi]

Support regex matching for tag/branches when parsing config/ci.json file. This is to allow using regex dev-.* patterns to specify test configuration for all dev branches, e.g.

{
    # ...
    "qa": {
        "dev-.*": { 
            "markers": "dev_config"
        },
        "default": {
           "markers": "config or dev_config"
       }
   },
   "default": { 
        # ....
    }
}

I added a python script for parsing the file so I could just use the standard python regex library for string matching. This meant it was also easier to add tests.

The order for finding a key's (e.g. "markers") value now is:

1. Exact match for branch/tag name in test type (e.g. qa)
2. Then first branch name matched with regex pattern for branch name in test type. This means a top-down ordering of regex patterns so would require more specific branch regex to be higher up in the list, e.g. dev-1deg-.* before dev-.*
3. Default for the test type (e.g. 'qa')
4. Top-level default

To avoid the composite action modifying the caller workflow environment, I've set update-environment: false in setup-python action, and called the python executable directly using the output of the action (see https://github.com/actions/setup-python/blob/main/docs/advanced-usage.md#using-update-environment-flag).

Similarly to avoid checking out the model-config-tests repository to obtain the parse-file.py file of the correct version, I am using github.action_path to access the files in the .github/actions/pares-ci-config directory (see https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs#github-context).

References #99