chore(participant): update namespace prompt, add additional accuracy tests VSCODE-583

[Anemy]

Part of VSCODE-583

Couple things in this pr:

• updated the namespace parsing regex to allow for just db or collection to be passed
• updated the namespace prompt to mention that just one can be supplied, with an example
• added a few more test datasets for the accuracy tests
• added 2 query tests (aggregation and a create index)
• added 4 namespace tests
• added schema passing for our query tests

I'm thinking this should reduce some of the namespace hallucinations. Will need more tests that get deeper into it to really know.

[nirinchev]

LGTM