Convert builtin errors to EvalErrors

[pgavlin]

This allows us to capture a stacktrace with the error so that failures
indicate the line of the failing expression.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 44.55%. Comparing base (73cf44e) to head (97795ae).

Files	Patch %	Lines
cmd/dawn/builtins.go	0.00%	5 Missing ⚠️
cmd/dawn/events.go	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main       #3      +/-   ##
==========================================
- Coverage   45.32%   44.55%   -0.77%     
==========================================
  Files          23       23              
  Lines        2716     2765      +49     
==========================================
+ Hits         1231     1232       +1     
- Misses       1348     1395      +47     
- Partials      137      138       +1     

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