Improve performance by reducing string copies

@Omega359 [mentioned in discord](https://discord.com/channels/885562378132000778/1344430130252218439/1415763431516278794) a blog post by the Databend folks about how they wrote a replacement of sqlparser-rs for their system

https://www.databend.com/blog/category-engineering/2025-09-10-query-parser/

One thing they cite is the fact that sqlparser-rs often copies strings, even when this could be avoided

If anyone cares, we can probably avoid copying strings, someone just has to care enough to thread the lifetime information through all the tokens (or maybe use an Arc w/ an offset)

@AdamGS mentioned he might be interested in trying this

This could possibly be related to another ticket here:
- https://github.com/apache/datafusion-sqlparser-rs/issues/1558

Start by reading the linked Databend blog post and related issue #1558, then inspect the lexer and token ownership paths to identify where strings are copied. Done means reducing avoidable string copies while preserving parser behavior and validating the performance impact with the project’s existing tests or benchmarks.

Written by the indexing model from the issue text.