Cast PostgreSQL's timestamptz columns to time

[lucasfais]

Before Rails 7, PostgreSQL's timestamptz columns were handled as datetime, but now type returns :timestamptz:

irb(main):181:0> User.columns_hash['created_at'].type
=> :timestamptz

I tested this PR's change in my production app, it's working fine, but let me know if this is not the correct/complete fix for the issue.

[scarroll32]

@lucasfais thank you for this PR.

Could you please add a couple of tests?

[lucasfais]

@scarroll32 Sure. Ransack::Nodes::Value had no specs, so I added basic specs for all types. :timestamptz specially is on line 28. Thanks!

[deivid-rodriguez]

Makes sense to me!

[scarroll32]

Thank you @lucasfais !