Remove discriminant code and support ftau in hlapi

[samvanstroud]

Summary

This pull request introduces the following changes

• Remove all discriminant calculatons / functions and use the implementation in atlas-ftag-tools
• Update the HLAPI and yuma with support for ftau

Relates to the following issues

• 223

Conformity

• [x] Changelog entry
• [x] Documentation

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (38d4a0b) 97.24% compared to head (316c856) 97.23%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #240 +/- ## ========================================== - Coverage 97.24% 97.23% -0.02% ========================================== Files 46 44 -2 Lines 4644 4591 -53 ========================================== - Hits 4516 4464 -52 + Misses 128 127 -1 ```

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