[feature] complete syntax about 'CREATE/DROP DATABASE Statement'

[hustjieke]

For CREATE DATABASE, MySQL 8.0 Syntax:

CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_option] ...

create_option: [DEFAULT] {
    CHARACTER SET [=] charset_name
  | COLLATE [=] collation_name
  | ENCRYPTION [=] {'Y' | 'N'}
}

Now in radon:

CREATE DATABASE [IF NOT EXISTS] db_name
    [create_option] ...

create_option: {
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
}

we should add support on SCHEMA and option ENCRYPTION

For DROP DATABASE, MySQL 8.0 syntax:

DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

Now in radon:

DROP DATABASE [IF EXISTS] db_name