feat(opensearch): support for updating ISM policy used for usage events

[darnaut]

Previously the ISM policy was never updated if it already existed. Now the policy is updated whenever elasticsearch-setup runs and the policy already exists. The response of the update operation is saved to a temporary directory for debugging purposes.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub