feat: Add filter_policy to astra integration

[vblagoje]

Why:

Adds flexible filtering options to astra integration. By introducing a filter policy option (replace or merge), developers can now control how runtime filters are applied relative to initialization time filters.

• partially fixes Add filter_policy init parameter to all retrievers #780
• supersedes feat: Add filter_policy init parameter to all retrievers #781

What:

• Added filter_policy parameter with options replace and merge across multiple retrievers to control filter behavior dynamically.
• Unit tests were updated or added to validate the new functionality.

How can it be used:

• Dynamic Filter Behavior Adjustment: Users can decide whether to completely override the initial filters set during the retriever's initialization (replace) or merge them with runtime filters, with the latter taking precedence (merge).

• Complex Search Scenarios:

  • In cases where the context of a query might dictate altering pre-set filters without discarding them, the merge option allows for an additive approach.
  • For strict query contexts that require ignoring initial filters, the replace option offers a clean slate for filters at runtime.

How did you test it:

• Unit tests were enhanced or newly created to cover both replace and merge scenarios for the filter_policy parameter.
• Tests ensure that filter logic is correctly applied based on the policy setting, whether it merges runtime filters with initial filters or replaces them entirely.
• Additional test cases should be considered for complex filter merge scenarios to ensure priority and override mechanisms function as expected.

[vblagoje]

Please delay review until a new patch release of 2.2.x is released. We need these two PRs to be included in a patch release first.