Add the ability to parse aggregations with OpenSearch

[kyle-sammons]

Summary

This PR adds the ability to parse aggregations with OpenSearch when the optional feature flag astra.query.useOpenSearchAggregationParsing is enabled. This follows the same pattern as the query refactor we did awhile back, keeping both the old parsing and new parsing paths in the code, and only switching between based on the feature flag. As such it should be reasonably inert and safe to deploy.

I also did some minor fixes to to the changes made in https://github.com/slackhq/astra/pull/1081, and added some tests; both of which were missed due to time constraints.

Requirements

• [X] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [X] I've read and agree to the Code of Conduct.

[bryanlb]

Closes #629

[bryanlb]

Closes #628