codeintel: VM-based indexer service

Created by: efritz

This PR creates a new service that does the work of indexing source code and uploading the resulting LSIF uploads to the instance. This service will be deployed outside of k8s for the cloud environment. Currently this implementation shells out to docker instead of firecracker so that we can ensure that the new indexer API and proxies are working correctly. We still only run lsif-go, which is considered trusted code.

In next steps, we will be removing the indexing code from the precise-code-intel-indexer service, renaming it to precise-code-intel-index-manager, and then renaming this new service precise-code-intel-indexer. We're doing this in multiple steps to prevent auto-indexing from stopping for a number of days during development/deployment.

This PR closes https://github.com/sourcegraph/sourcegraph/issues/12707.