Validate scriban on new notifications

[tevoinea]

Summary of the Pull Request

What is this about?

Closes #2837

We should validate notification configs at creation time that they can be safely rendered by scriban.

• Move some scriban conversion utility functions to JinjaTemplateAdapter.cs
• Validate templates are compatible with scriban at notification creation time by:
  • Seeing if we need to apply any migrations to it
  • It can be rendered by scriban without throwing
• Update integration tests to support using feature flags

[codecov-commenter]

Codecov Report

Merging #2834 (beb7fd3) into main (21374b3) will decrease coverage by 0.03%.
The diff coverage is 43.67%.

@@            Coverage Diff             @@
##             main    #2834      +/-   ##
==========================================
- Coverage   29.87%   29.84%   -0.03%     
==========================================
  Files         324      324              
  Lines       39062    39130      +68     
==========================================
+ Hits        11671    11680       +9     
- Misses      27391    27450      +59     

Impacted Files	Coverage Δ
...ApiService/ApiService/Functions/ValidateScriban.cs	0.00% <0.00%> (ø)
...e/onefuzzlib/notifications/JinjaTemplateAdapter.cs	44.82% <43.04%> (-55.18%)	⬇️
...ce/ApiService/onefuzzlib/NotificationOperations.cs	28.71% <66.66%> (+1.16%)	⬆️
.../ApiService/Functions/Migrations/JinjaToScriban.cs	80.00% <100.00%> (-12.40%)	⬇️

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