Add a new JSON field "version_id" into mysql.global_priv.priv

Under terms of MDEV-21743, we'll add new global privilege flags.
In order to help the server understand which version a privilege record was written by, let's add a new JSON field "version_id" in mysql.global_priv.priv.

So the following script:

GRANT FILE ON *.* TO user1@localhost;

SELECT Host, User, JSON_DETAILED(Priv) FROM mysql.global_priv WHERE user='user1'\G

returns about this output:

*************************** 1. row ***************************

               Host: localhost

               User: user1

JSON_DETAILED(Priv): {

    "access": 512,

    "plugin": "mysql_native_password",

    "authentication_string": "",

    "password_last_changed": 1581070979,

    "version_id": 100502

}

1 row in set (0.001 sec)

Notice, the new "version_id" field in the JSON record.

The version id is needed to translate a set of bits to a set of privileges.

If the version_id JSON field is missing in a record, the server will consider that this record was created by MariaDB-10.5.1 or earlier.

As version_id is determined per record, records of different formats will co-exist in the same table without conflicts, so no mysql_upgrade execution will be needed to make the global_priv table up-to-date after upgrade to a new server version with new privilege bits defined.

If the version_id JSON field is missing in a record, the server will consider that this record was created by MariaDB-10.5.1 or earlier.

As version_id is determined per record, records of different formats will co-exist in the same table without conflicts, so no mysql_upgrade execution will be needed to make the global_priv table up-to-date after upgrade to a new server version with new privilege bits defined.

This change will also include:

• Validation for the new "version_id" JSON field, to ignore records with obviously wrong version_id records.
• Validation for the "access" JSON field, to ignore records when "access" has any bits set which are not known as of server version specified in version_od
• Reporting ignored records to the server error log.