chore: Bump Rust toolchain

[MazterQyou]

This PR bumps Rust toolchain to nightly-2023-12-13, following cubesql bump. rust-toolchain is also migrated to TOML format.

[coveralls]

Pull Request Test Coverage Report for Build 7257830118

• 45 of 48 (93.75%) changed or added relevant lines in 13 files are covered.
• 34 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-4.3%) to 85.164%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser.rs	3	6	50.0%

Files with Coverage Reduction	New Missed Lines	%
tests/sqlparser_mysql.rs	2	99.25%
tests/sqlparser_common.rs	15	96.5%
src/parser.rs	17	82.7%

Totals
Change from base Build 7141689314:	-4.3%
Covered Lines:	9081
Relevant Lines:	10663

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💛 - Coveralls