GDK automation for running Zoekt

We should allow users to add zoekt: true to their gdk.yml file and have this automatically start 4 Zoekt servers (2 for test, 2 for dev) like so:

  1. zoekt-dynamic-indexserver -data_dir zoekt/test/data -index_dir zoekt/test/index -listen :6060
  2. zoekt-webserver -index zoekt/test/index -rpc -listen :6070
  3. zoekt-dynamic-indexserver -data_dir zoekt/dev/data -index_dir zoekt/dev/index -listen :6080
  4. zoekt-webserver -index zoekt/dev/index -rpc -listen :6090

We should also build the following Zoekt binaries in GDK for you automatically (following the same approach we use for gitlab-elasticsearch-indexer):

  1. zoekt-git-index
  2. zoekt-git-clone
  3. zoekt-dynamic-indexserver
  4. zoekt-webserver

When we have this we can tidy up some docs added in #389757 (closed) to simplify the steps.

Edited by Dylan Griffith (ex GitLab)