Add random function

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (79af2d0) 78.89% compared to head (c8bf023) 78.84%.

Files	Patch %	Lines
internal/expr/functions/math.go	0.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #514 +/- ## ========================================== - Coverage 78.89% 78.84% -0.05% ========================================== Files 126 126 Lines 10905 10909 +4 ========================================== - Hits 8603 8601 -2 - Misses 1578 1584 +6 Partials 724 724 ```

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