Add support for schema validation for X plugin's admin commands.
Existing 'create_collection' and 'ensure_collection' admin commands are
extended to support new schema argument. Two new admin command are added
to facilitate working on collections - 'modify_collection_options' and
'get_collection_options'.

Validation schema which is set during collection creation may have two
validation levels: 'strict' and 'off'. When validation is set as 'strict'
each operation on a collection is validated against the validation schema.
Validation schema and validation level for existing collections may be
modified using the 'modify_collection_options' command and retrieved by
the 'get_collection_options' command.

RB: 22168
Reviewed by: Grzegorz Szwarc <grzegorz.szwarc@oracle.com>
Reviewed by: Lukasz Kotula <lukasz.kotula@oracle.com>

Approved by: Ashish Padiyar <ashish.padiyar@oracle.com>