fix: check to make sure index exists before adding a policy

[robert-sorkin]

Description

•Recreating PR due to monorepo changes. Original PR: https://github.com/camunda/operate/pull/6641

•Added check to see if index exists
•Added some unit tests to ElasticsearchArchiveRepository and OpensearchArchiveRepository

Related issues

closes https://github.com/camunda/operate/issues/5921

Definition of Done

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Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix to the last two minor versions. You can trigger a backport by assigning labels (e.g. backport stable/1.3) to the PR, in case that fails you need to create backports manually.

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually
• The change has been verified by a QA run
• The impact of the changes is verified by a benchmark

Documentation:

• The documentation is updated (e.g. BPMN reference, configuration, examples, get-started guides, etc.)
• If the PR changes how BPMN processes are validated (e.g. support new BPMN element) then the Camunda modeling team should be informed to adjust the BPMN linting.

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• Tasklist
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[github-actions]

Test Results

974 tests   938 ✅  2h 30m 32s ⏱️
170 suites   36 💤
170 files      0 ❌

Results for commit 59be482.

♻️ This comment has been updated with latest results.