Replace `proof-of-sql-parser` with `sqlparser`.

[JayWhite2357]

Background and Motivation

Currently, we have an in-house parser that is built on the lalrpop parser-generator. This has been good while the supported syntax has been simple. However, as the supported syntax has grown, we need a more comprehensive parser.

The sqlparser crate is the parser used by DataFusion, which is part of the Arrow ecosystem. It is a feature-rich parser that ultimately will require less code maintenance. It is no_std compatible, so there should be no issues integrating it.

Changes Required

• [ ] Replace proof-of-sql-parser usage within the proof-of-sql crate with sqlparser usage.
• [ ] Ensure that no functionality is removed.
• [ ] Add thorough testing.
• [ ] Remove the workspace and simplify the repo to be a single crate: the proof-of-sql crate.