Revert GUID type deprecation

[morozov]

The APIs related to the GUID column type were mistakenly deprecated in #4724. There are two features in the DBAL related to the GUID type:

1. Generation of UUID values on the DB side (deprecated in Deprecated usage of DB-generated UUIDs #3212).
2. Storing UUID values in the database (mistakenly deprecated).

The purpose of the GUID column type in the DBAL is:

1. Provide a way to store UUID values efficiently on the platforms that support it natively (PostgreSQL, SQL Server). These platforms will store the value in a binary format (effectively, BINARY(16)) and provide automatic parsing and formatting for a better developer experience.
2. Enable the rest of the platforms to store the UUID value as CHAR(36). This is way less efficient from the storage and lookup perspective than the above but still works.

Without this type in place, the users would have to use either BINARY(16) or CHAR(36) to write portable code which will result in a worse developer experience on the platforms that support the type natively.

Additionally, a functional test is added that covers the type across all supported platforms and identifies a minor inconsistency in their behavior.