Enhance TF for new DMS and DMS API v2

[cboelle]

Description of the enhancement

For the users of the new DMS service it will be important to:
• Configure number of brokers (new flexibility)
• Create new single instances
• Create new Kafka 3.x clusters

https://registry.terraform.io/providers/opentelekomcloud/opentelekomcloud/latest/docs/resources/dms_instance_v2

Current issues:

• Current version seems using v1 data source (to specify product_id) which is not compatible
• engine_version 3.4 should be listed in documentation and be used as new default
• New optional broker number is needed to extend cluster to 4,5,6, … brokers during instance creation
• New examples needed: 1 for single instance and 1 for kafka 3.x cluster

[anton-sidelnikov]

Hi @cboelle, duplicate of #2596, we already updated DMS resources, please wait for next releases.

[anton-sidelnikov]

@artem-lifshits please update documentation and add extra examples