fix: Fix .apply serialization error with optional structs

[Natoandro]

• Fix the error on .apply when the apply tree goes beyond an optional struct, mostly changing the implementation of resolve_optional method.
• Improve the errors when we encounter an exception raise by Result::Err from typegraph_core.

Migration notes

...

• The change comes with new or modified tests
• Hard-to-understand functions have explanatory comments
• End-user documentation is updated to reflect the change

[codecov]

Codecov Report

Attention: Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 76.77%. Comparing base (7c52fce) to head (85862c2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/typegraph/deno/src/typegraph.ts	0.00%	7 Missing ⚠️
src/typegraph/deno/src/types.ts	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #886      +/-   ##
==========================================
- Coverage   76.80%   76.77%   -0.04%     
==========================================
  Files         149      149              
  Lines       18224    18233       +9     
  Branches     1769     1768       -1     
==========================================
+ Hits        13997    13998       +1     
- Misses       4204     4212       +8     
  Partials       23       23              

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