parser: Complete rewrite to LALR

[elliotchance]

This replaces the existing Earley parser (which is O(n^3)) with a LALR parser using Yacc which is an ideal O(n). Even with very short SQL statements, the existing parser was really slow, so I had to build a query cache as bandaid, but that has also been removed now.

This refactoring was made possible by adapting yacc from a Go implementation here: https://github.com/elliotchance/vyac. However, in keeping with the promise of this repo being completely written in V, the source has been copied to this repo.

Other notable and breaking changes:

1. Not sure how this worked before, but the query may not specify a catalog in identity chains (for example, catalog.schema.table). The catalog must be set using SET CATALOG.
2. Syntax error messages will be slightly different, but should be a little more helpful.
3. There are some ambiguities with the SQL grammar, such as trying to decode what x IS NOT TRUE means or differentiating between COUNT(expr) vs COUNT(*) due to lookahead limitations. Some special tokens for combinations of operators and keywords have had to be added for known edge cases, but there are many remaining conflicts. I suspect these conflicts don't matter as ambiguous paths should still yield valid results, so these warnings have to be ignored for now.
4. Fixes a very minor bug where string literals in VALUES might be treated as VARCHAR instead of CHARACTER in some cases.
5. Renamed "std_" files with their position number in the standard. This helps for grouping similar sections and makes lookups easier.