sqlite: refactor error helpers and user function pointers

[thisalihassan]

Two small independent refactors.

1. Consolidate CreateSQLiteError overloads
2. BaseObjectWeakPtr for user functions (style consistency)

[nodejs-github-bot]

Review requested:

• @nodejs/sqlite

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.68%. Comparing base (4e612c0) to head (3162244).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_sqlite.cc	88.88%	1 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62794      +/-   ##
==========================================
- Coverage   89.69%   89.68%   -0.02%     
==========================================
  Files         706      706              
  Lines      218247   218252       +5     
  Branches    41777    41782       +5     
==========================================
- Hits       195760   195730      -30     
- Misses      14401    14438      +37     
+ Partials     8086     8084       -2     

Files with missing lines	Coverage Δ
src/node_sqlite.h	80.64% <ø> (ø)
src/node_sqlite.cc	80.78% <88.88%> (+0.05%)	⬆️

... and 33 files with indirect coverage changes

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