db: fix db.Initialize() sqlite3 error checking, add errortype linter

[cce]

Summary

While working on #6466, I discovered a bug where error-handling wasn't working as I intended because I was misusing errors.As on a pointer error-type (that implemented the error interface using value receiver methods).

This errortype linter would have caught the bug, added here to our custom warning linter.

It also caught a similar bug handling sqlite3.Error in util/db/initialize.go, fixed here.

Test Plan

Existing tests should pass.

[Copilot]

Pull Request Overview

This PR fixes a bug in SQLite error handling and adds the errortype linter to prevent similar issues in the future. The bug involved incorrectly using errors.As with a pointer type for sqlite3.Error, which doesn't implement the error interface via pointer receiver methods.

• Fixed sqlite3.Error type declaration in util/db/initialize.go from pointer to value type
• Added errortype linter configuration to catch error handling bugs
• Updated TransactionInLedgerError.Error() to use pointer receiver for consistency
• Added compile-time checks verifying error interface implementations

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
util/db/initialize.go	Changed sqlite3.Error from pointer to value type to fix errors.As usage
ledger/ledgercore/error.go	Added error interface verification checks and changed TransactionInLedgerError.Error() to pointer receiver
.golangci-warnings.yml	Added errortype linter configuration with appropriate settings
.custom-gcl.yml	Added errortype plugin dependency configuration

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 47.28%. Comparing base (9dc5156) to head (cffe002).
⚠️ Report is 5 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
ledger/ledgercore/error.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6477      +/-   ##
==========================================
+ Coverage   47.05%   47.28%   +0.22%     
==========================================
  Files         667      659       -8     
  Lines       88831    88225     -606     
==========================================
- Hits        41802    41713      -89     
+ Misses      44284    43745     -539     
- Partials     2745     2767      +22     

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[algorandskiy]

Good catch!