feat: add mysql right function

[raspberry-hu]

What this PR does:

Which issue(s) this PR fixes:

Fixes #519

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-commenter]

Codecov Report

Base: 36.59% // Head: 36.61% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (167875a) compared to base (0d0d7ab).
Patch coverage: 60.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #528      +/-   ##
==========================================
+ Coverage   36.59%   36.61%   +0.02%     
==========================================
  Files         165      166       +1     
  Lines       21675    21690      +15     
==========================================
+ Hits         7931     7942      +11     
- Misses      12877    12878       +1     
- Partials      867      870       +3     

Impacted Files	Coverage Δ
pkg/runtime/function/right.go	60.00% <60.00%> (ø)
pkg/schema/loader.go	6.74% <0.00%> (+1.12%)	⬆️

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