Signed int parse

[GuptaManan100]

Description

The following query does not work correctly in the parser

alter table t add column iii int signed not null;

This PR fixes it by adding the optional SIGNED token after the numeric type names.

Related Issue(s)

Fixes #8153

Checklist

• Tests were added or are not required
• Documentation was added or is not required

[shlomi-noach]

Does this need support in ast_print.go?

[systay]

We should not drop the signed/unsigned part in the AST

[GuptaManan100]

We are already storing the signed/unsigned part in the AST. Its just that signed is the default so it is dropped. Since we already had the functionality of storing this in AST, we do not require any changes to ast_format.go. I have added a test which checks that we indeed do not ignore unsigned.

[shlomi-noach]

sounds good