codeintel: Add rich indexer to lsif upload/indexer types

Created by: efritz

This adds an indexer field as a sibling to inputIndexert on both lsif uploads and indexes. We will try to match these values against a known indexer so that we can give additional information in the frontend about the tool.

Immediately, we'll be able to expose a link to the indexer hompage, which is already a huge plus.

Test plan

Tested locally by hand.