feat: add run async filter and automerging retriever

[OscarPindaro]

Related Issues

• fixes Add run_async method to FilterRetriever and AutoMergingRetriever #9896

Proposed Changes:

Now FilterRetriever and AutoMergingRetriever both support the async method run_async.
The code in run_async is copied from the run method, except for the calls to the document store and async helper functions that have been marked and called accordingly with the async/await keywords.

How did you test it?

For each retriever, I created a copy of the original tests adding the suffix _async at the end of the filename.
I kept the fixtures from the original file, so there is some duplication.
I kept only the tests regarding the run method, ignoring the initialization tests (since they are not affected by this PR).
FilterRetriever had an integration test, so I wrote the equivalent async one.
AutoMergingRetriever does not have any integration tests.

Notes for the reviewer

run and run_async share a lot of code, but I was cautious because I don't know if you expect me to refactor shared logic into separate functions to avoid the duplication. If that's the case, I'm happy to do that.

Unfortunately, the type checking is failing since the general DocumentStore class does not support the async filtering method. The tests are passing because they are using InMemoryDocumentStore, which actually has that method.

> hatch run test:types
haystack/components/retrievers/filter_retriever.py:107: error: "DocumentStore" has no attribute "filter_documents_async"; maybe "filter_documents"?  [attr-defined]
haystack/components/retrievers/auto_merging_retriever.py:187: error: "DocumentStore" has no attribute "filter_documents_async"; maybe "filter_documents"?  [attr-defined]
Found 2 errors in 2 files (checked 257 source files) 

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes
• I documented my code
• I ran pre-commit hooks and fixed any issues

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Pull Request Test Coverage Report for Build 18635856245

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 92.218%

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Totals
Change from base Build 18597051353:	0.02%
Covered Lines:	13378
Relevant Lines:	14507

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💛 - Coveralls