bugfix: Update list method return types to use list[list[OutputData]] for vector stores

[AlinMH]

Description

Vector store list method returns a list of lists for most of the cases expect for qdrant which is returning a tuple, this PR fixes the type hinting and the type checks.

Fixes #2764 (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

I've tested manually with an Elasticsearch vector store, the actual tests are not doing that, I might need help with these unit tests.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx (Replace xxxx with the GitHub issue number)
• Made sure Checks passed

[CLAassistant]

All committers have signed the CLA.