Add support for Elasticsearch Platinum

[omaraibrahim]

Community Note

• Please vote on this pull request by adding a 👍 reaction to the original pull request comment to help the community and maintainers prioritize this request
• Please do not leave "+1" or other comments that do not add relevant new information or questions, they generate extra noise for pull request followers and do not help prioritize the request

This PR is for making elasticsearch platinum available on terraform.

Output from acceptance testing:

$ make testacc TEST=./ibm/service/database TESTARGS='-run=TestAccIBMDatabaseInstance_ElasticsearchPlatinum_Basic'
--- PASS: TestAccIBMDatabaseInstance_ElasticsearchPlatinum_Basic (1375.52s)
PASS
ok  	github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/database	1380.582s
...

[kavya498]

Please update docs and secret.baseline file

[obai-1]

@omaraibrahim could you add a sample for platinum instance, like this one https://registry.terraform.io/providers/IBM-Cloud/ibm/latest/docs/resources/database#sample-elasticsearch-enterprise-instance