chore: mustache clean up

[tusharmath]

• split mustache into smaller modules
• add eval for mustache
• move render implementation into eval
• restructure tests

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.74419% with 14 lines in your changes missing coverage. Please review.

Project coverage is 85.71%. Comparing base (8a7dd73) to head (9c167c1).

Files	Patch %	Lines
src/core/mustache/eval.rs	92.97%	13 Missing :warning:
src/core/mustache/parse.rs	99.51%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2280 +/- ## ========================================== - Coverage 85.74% 85.71% -0.03% ========================================== Files 219 221 +2 Lines 21022 21036 +14 ========================================== + Hits 18025 18031 +6 - Misses 2997 3005 +8 ```

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