List licenses of all the dependencies and enforce license check in CI

As `connectors-python` repo is an open source repo, and connector service is released as a product, it's important that it follows [Elastic Open Source Policy](https://github.com/elastic/open-source/blob/main/elastic-product-policy.md
)

### Acceptance criteria

- [ ] Add a `deps-licenses.md` file to list licenses of all the dependencies
- [ ] Add a make target to update `deps-licenses.md`
- [ ] Add a CI check to make sure `deps-licenses.md` is up to date

#### Stretch
- [ ] Add a CI check to make sure the licenses of all the dependencies are from the [green list](https://github.com/elastic/open-source/blob/main/elastic-product-policy.md#green-list)