refactor: add batch_size to FAISS __init__

[pandasar13]

Related Issues

• fixes Add batch_size to FAISS __init__ #6381

Proposed Changes:

Added batch_size to the init method of FAISSDocumentStore and modified the functions that use batch_size to either specify batch_size or use self.batch_size.

This way batch_size can be specified in the init method, being consistent with other document stores (e.g. Weaviate, Opensearch)

How did you test it?
manual verification

Notes for the reviewer
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:.
I documented my code
I ran pre-commit hooks and fixed any issue

[julian-risch]

@pandasar13 Could you please move the release note you created to releasenotes//notes/add-batch_size_faiss_init-5e97c1fb9409f873.yaml Currently it is in releasenotes/notes/releasenotes/notes/add-batch_size_faiss_init-5e97c1fb9409f873.yaml
In the note, you can leave out all the other sections and just put your note in the enhancements sections. We use the upgrade section for changes where we would like to advise the users how to migrate.

[coveralls]

Pull Request Test Coverage Report for Build 6972059698

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 143 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.06%) to 40.214%

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Files with Coverage Reduction	New Missed Lines	%
nodes/file_converter/init.py	1	88.89%
document_stores/faiss.py	142	18.35%

Totals
Change from base Build 6971350954:	0.06%
Covered Lines:	10688
Relevant Lines:	26578

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💛 - Coveralls

[anakin87]

Looks good to me.

Thanks for your 1st contribution to Haystack! 💟

I will merge this PR when the tests pass...