Implements ALTER POLICY syntax for PostgreSQL

[git-hulk]

ALTER POLICY name ON table_name RENAME TO new_name

ALTER POLICY name ON table_name
    [ TO { role_name | PUBLIC | CURRENT_ROLE | CURRENT_USER | SESSION_USER } [, ...] ]
    [ USING ( using_expression ) ]
    [ WITH CHECK ( check_expression ) ]

For the documentation, please refer:

https://www.postgresql.org/docs/current/sql-alterpolicy.html

[coveralls]

Pull Request Test Coverage Report for Build 11091759958

Details

• 76 of 90 (84.44%) changed or added relevant lines in 5 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.01%) to 89.31%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ast/ddl.rs	14	16	87.5%
src/ast/mod.rs	4	6	66.67%
tests/sqlparser_common.rs	24	34	70.59%
<!--	Total:	76	90	84.44%	-->

Files with Coverage Reduction	New Missed Lines	%
src/ast/mod.rs	1	82.39%
src/parser/mod.rs	1	93.35%
<!--	Total:	2		-->

Totals
Change from base Build 11091694888:	-0.01%
Covered Lines:	29901
Relevant Lines:	33480

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💛 - Coveralls

[git-hulk]

cc @iffyio

[alamb]

I merged up from main to resolve a conflict

[git-hulk]

@alamb Thank you!

[alamb]

🚀