Fix part of #5343: Update the test exemption check script & its exemp…

…tion format (#5426)

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Fixes part of #5343

**Project**
[PR 1.2 of Project 4.1]
This PR is based on develop as it had no other dependency with other
PRs.

### Changes Implemented
This PR implements updates to enhance the handling of file exemptions
and code coverage settings:

1. Updates `script_exemptions.proto` to support two possible states:
   - Exemption from requiring a test file (current behavior).
- Override of the minimum code coverage to meet a specific percentage
(including 0%).

2. Aligns `test_file_exemptions.textproto` with the new proto format.

3. Modifies `TestFileCheck.kt` to integrate the updated proto format.

## Project Context
In Project 4.1, we are introducing code coverage capabilities where
certain files may require exemptions from the default minimum code
coverage percentage. These exemptions can now be managed in
`test_file_exemptions.textproto` by setting the
`override_min_coverage_percentage`.

## Implementation Details
Initially, I explored using the `TodoOpenCheck` regeneration structure
to implement these changes. However, due to significant differences in
regeneration requirements (creating a new proto format to regenerate the
exemptions list), conflicts arose with
`generate_test_file_assets_list_from_text_protos`.

Given that the regeneration process is solely aimed at rebuilding the
textproto file and no longer serves any other purpose in this project, I
opted to manually compile a list of exempted files and used it to
generate the new proto format. I then transferred this newly generated
format to the textproto file. The regeneration implementation can be
found in my [local test_exemption
branch](Rd4dev@189a1da#diff-fd100a053f2b965df76d989b0d97b5400c051c7fff9507afc0d891cfaf36e238R925)

Post-generation, the regeneration functionality was removed, as it no
longer aligns with the project's needs. Further validation and
adjustments, if necessary, will be discussed with Ben and implemented.


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---------

Co-authored-by: Ben Henning <[email protected]>