Optionally install OpenSearch helm chart with Bitbucket

[bianchi2]

This PR adds an optional deployment of OpenSearch cluster together with the Bitbucket Helm chart:

• disabled by default
• if enabled starts a 1 node cluster, ssl disabled
• if enabled, Bitbucket will be automatically configured to use this cluster for search (setting PLUGIN_SEARCH* env vars)
• by default admin users is created, password is auto-generated
• it is possible to provision custom internal users file to create dedicated users and set admin password
• ssl is disabled by default, docs explain how to provide custom certificates and optionally add ca to Java trust store in Bitbucket containers

Checklist

• [x] I have added unit tests
• [x] I have applied the change to all applicable products
• [x] The E2E test has passed (use e2e label)