Lt22416 Move Allomorph generator into the FLEx repo

[AndyBlack]

This is for LT-22416 (Move Allomorph generator into the FLEx repo).

This contains two FLEx add-on utilities that have been in production use by a few FLEx users for some time now. The changes here moved what was in the GitHub repository at https://github.com/sillsdev/FLExAllomorphGenerator to Src\Utilities. The utilities are:

1. Allomorph Generator for FLEx: A tool to generate allomorphs for a FLEx project based on the citation form, the lexeme form, the etymology form, or an entry-level custom field of an entry.
2. Variant Generator for FLEx: A tool to generate variants for a FLEx project based on the citation form, the lexeme form, the etymology form, or an entry-level custom field of an entry.

There also is a ReadMe.txt file pointing to the soon-to-be-archived repository mentioned above in case some one needs to check its history.

Note that the code in that repository that is now in FLEx has never undergone a human code review. I did ask devin.ai to review it and made most of the fixes/changes it noticed.

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This change is 

[github-actions]

NUnit Tests

    1 files  ±0      1 suites  ±0   6m 4s ⏱️ -1s
4 414 tests +7  4 327 ✅ +7  87 💤 ±0  0 ❌ ±0 
4 423 runs  +7  4 336 ✅ +7  87 💤 ±0  0 ❌ ±0 

Results for commit 78c72c7. ± Comparison against base commit 0756d4f.