[FSTORE-1202] Support similarity search in external fg

[kennethmhc]

This PR adds/fixes/changes...

• please summarize your changes to the code
• and make sure to include all changes to user-facing APIs

JIRA Issue: -

Priority for Review: -

Related PRs: -

How Has This Been Tested?

• Unit Tests
• Integration Tests
• Manual Tests on VM

Checklist For The Assigned Reviewer:

- [ ] Checked if merge conflicts with master exist
- [ ] Checked if stylechecks for Java and Python pass
- [ ] Checked if all docstrings were added and/or updated appropriately
- [ ] Ran spellcheck on docstring
- [ ] Checked if guides & concepts need to be updated
- [ ] Checked if naming conventions for parameters and variables were followed
- [ ] Checked if private methods are properly declared and used
- [ ] Checked if hard-to-understand areas of code are commented
- [ ] Checked if tests are effective
- [ ] Built and deployed changes on dev VM and tested manually
- [x] (Checked if all type annotations were added and/or updated appropriately)

[vatj]

Please document the not straightforward behaviour of the .read method for fg has an embedding column and online=True. It should appear in both the docstring and I would suggest the error message as well. Point towards the show method in this case

[vatj]

read_options should default to None and get initialised in the function body to make sonarlint happy :). Additionally read_options is not used in the function, did you forget to add it to the query.read method?

[vatj]

Looks good, smart thinking to move splitting the ux decision to a different JIRA to move forward and get the PR merged