Propagate AST errors to the user

[hansl]

This gives better error messages:

Prior to this PR, the message would simply say "invalid scope analysis" without any further reason.

[codecov]

Codecov Report

❌ Patch coverage is 44.00000% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.69%. Comparing base (6ddc2b4) to head (cef9654).
⚠️ Report is 518 commits behind head on main.

Files with missing lines	Patch %	Lines
core/ast/src/source.rs	58.33%	5 Missing ⚠️
core/parser/src/parser/mod.rs	0.00%	4 Missing ⚠️
core/ast/src/function/ordinary_function.rs	0.00%	2 Missing ⚠️
core/ast/src/scope_analyzer.rs	66.66%	2 Missing ⚠️
core/engine/src/builtins/function/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4408      +/-   ##
==========================================
+ Coverage   47.24%   50.69%   +3.45%     
==========================================
  Files         476      512      +36     
  Lines       46892    51356    +4464     
==========================================
+ Hits        22154    26035    +3881     
- Misses      24738    25321     +583     

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[nekevss]

Nice work!