feat(dialects): add Exasol support

[benfdking]

Summary

• add the Exasol lexer, keywords, grammar, dialect registration, and documentation
• port all 60 Exasol SQLFluff fixture pairs from the currently pinned SQLFluff commit
• integrate Exasol-specific rule behavior for bare UNION, script-body indentation, and password literals
• keep this as a separate prerequisite PR before advancing the SQLFluff stack in chore: standardize databricks test fixture names (#4955) #3034

SQLFluff snapshot

This ports Exasol as it exists at the repository's current pinned SQLFluff SHA:

4a9152d3acda887aed551800b8c3a8833d72bd5e

.sqlfluff-sha is intentionally unchanged.

Verification

• cargo test -p sqruff-lib-dialects --test dialects -- exasol (60/60 fixture files)
• cargo check --workspace --all-features
• /etc/profiles/per-user/ben/bin/bazelisk test //... --test_output=errors (33/33 Bazel test targets pass)

[github-actions]

Benchmark for c38cf26

Click to view benchmark

Test	Base	PR	%
DepthMap::from_parent	116.6±1.16µs	112.9±2.82µs	-3.17%
fix_complex_query	13.2±0.10ms	13.7±0.11ms	+3.79%
fix_superlong	125.3±9.31ms	150.6±10.21ms	+20.19%
parse_complex_query	4.1±0.06µs	4.1±0.04µs	0.00%
parse_expression_recursion	7.0±0.09µs	7.3±0.06µs	+4.29%
parse_simple_query	1059.8±16.10ns	1053.9±18.28ns	-0.56%