Improve warnings is transcript selection errors

[Peter-J-Freeman]

This commit adds error codes to existing transcript selection warnings. It also now warns if a transcript variant is submitted with a non-matching transcript selection, rather than the old behavior which resulted in a lost result and could become empty.

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.33%. Comparing base (9c292f6) to head (94f0fd4).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
VariantValidator/modules/mappers.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #846   +/-   ##
========================================
  Coverage    76.32%   76.33%           
========================================
  Files           37       37           
  Lines        13054    13059    +5     
========================================
+ Hits          9964     9968    +4     
- Misses        3090     3091    +1     

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[John-F-Wagstaff]

That looks good, if Raymond is happy with the output then this is good to go in.

[Peter-J-Freeman]

I took Raymond's guidance. So will pull it in