feat: add mysql show status statement

[invm]

Hi,

Wanted to add support for SHOW [GLOBAL | SESSION] STATUS [LIKE 'pattern' | WHERE expr]

Taken from: mysql docs

[coveralls]

Pull Request Test Coverage Report for Build 7714670421

• -4 of 34 (88.24%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.001%) to 87.659%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ast/mod.rs	12	14	85.71%
src/parser/mod.rs	4	6	66.67%

Files with Coverage Reduction	New Missed Lines	%
src/ast/mod.rs	1	79.44%

Totals
Change from base Build 7660582105:	0.001%
Covered Lines:	19512
Relevant Lines:	22259

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💛 - Coveralls

[alamb]

Looks good to me -- thank you for the contribution @invm