fix(parser): reset popped lexer errors when rewinding

[ulrichstark]

Closes #12816.
Alternative to #13460.

This PR is the slightly cleaner way to fix the issue compared to the other PR, but comes at a potential performance cost because now instead of remembering how many errors there were, we are storing a clone of all errors and re-assign them when rewinding.

This makes it possible to fix the issue because now even errors before a checkpoint, that were popped/removed after the checkpoint, are properly rewinded.

[Copilot]

Pull Request Overview

Fixes a lexer rewinding bug where popped errors before a checkpoint weren't properly restored when rewinding. This changes the error handling strategy from storing an error count to storing a complete clone of all errors.

• Modifies LexerCheckpoint to store a full clone of errors instead of just the error count
• Updates checkpoint creation and rewinding methods to use the new error cloning approach
• Renames position field to source_position for clarity

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13494 will not alter performance

_{Comparing ulrichstark:even-reset-popped-lexer-errors-when-rewinding (cdd7466) with main (dc9645f)}

Summary

✅ 37 untouched benchmarks

[ulrichstark]

Some parser benchmarks improved and some regressed. Interesting... This makes this solution even better.