Support the ARRAY type of Snowflake

[yuval-illumex]

According snowflake documentation, There is an ARRAY type.
Behind the scenes it contains the VARIANT Data type, but the syntax is different. Snowflake don't support VARIANT[].
The query that I want to support is: SELECT CAST (a as array)
I started with creating a new data type called SnowflakeArray, But I think it's better to use the existing ARRAY data type (which created for the HIVE dialect)

[coveralls]

Pull Request Test Coverage Report for Build 3389576674

• 27 of 27 (100.0%) changed or added relevant lines in 5 files are covered.
• 234 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.01%) to 85.997%

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Files with Coverage Reduction	New Missed Lines	%
src/lib.rs	2	10.0%
src/parser.rs	10	83.77%
tests/sqlparser_postgres.rs	23	97.81%
src/ast/mod.rs	199	77.07%

Totals
Change from base Build 3379170887:	0.01%
Covered Lines:	11048
Relevant Lines:	12847

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💛 - Coveralls

[alamb]

Thank you for the contribution @yuval-illumex

[alamb]

I would prefer if this didn't add VARAINT into the parse tree when it wasn't in the original syntax. Can we model this like DataType::Array(None) perhaps?

[yuval-illumex]

@alamb I change the data type to be Array(Option<Box<DataType>>) to accept None.
I don't think it breaks anything but waiting to your feedback :) (I'm new to Rust).

Thank you!

[alamb]

Looks good to me -- thanks @yuval-illumex