Support Google Gemini API as a Provider

[adhintz]

Copying from @shanehuntley's original issue in the previous repo:

Support Google Gemini as a provider via Gemini API
https://ai.google.dev/gemini-api

Remaining tasks from the PR review:

• change to vcr tests. @codefromthecrypt has done this in test: convert Google Gemini tests to VCR #118
• try vision model. Requires the images to be encoded.
• add to pyproject.toml
• add vcr tests for vision. @codefromthecrypt has done this in test: add VCR tests for google vision adhintz/goose#1

[lily-de]

Looks like this can be closed? Latest merged PR seems to the the VCR tests for vision

[codefromthecrypt]

has integration tests, but not the vcr ones. they'll be in soon