Sqlfluff rewritten in Rust: ~10x speed improvement

TL;DR: Sqlfluff rewritten in Rust, about 10x speed improvement and portable

At[Quary](https://www.quary.dev/), we're big fans of [SQLFluff](https://sqlfluff.com/)! It's the most comprehensive formatter/linter about! It outputs great-looking code and has great checks for writing high-quality SQL.

That said, it can often be slow, and in some CI pipelines, we've seen it be the slowest step. To help us and our customers, we decided to rewrite it in Rust to get faster performance and portability so that we could run it anywhere.

Sqruff currently supports the following dialects: ANSI, BigQuery, and Postgres, and we are working on the next Snowflake and Clickhouse.

In terms of performance, we tend to see about 10x speed improvement for a single file when run in the sqruff repo:

    time sqruff lint crates/lib/test/fixtures/dialects/ansi/drop_index_if_exists.sql
    0.01s user 0.01s system 42% cpu 0.041 total
            
    time sqlfluff lint crates/lib/test/fixtures/dialects/ansi/drop_index_if_exists.sql
    0.23s user 0.06s system 74% cpu 0.398 total

And for a whole list of files, we see about 9x improvement depending on what you measure:

    time sqruff lint crates/lib/test/fixtures/dialects/ansi    
    4.23s user 1.53s system 735% cpu 0.784 total
        
    time sqlfluff lint crates/lib/test/fixtures/dialects/ansi
    5.44s user 0.43s system 93% cpu 6.312 total

Both tests were run on an M1 Mac.