symbols: do not rely on ctags.d

Created by: keegancsmith

We have regressed on this before by having .ctags.d in the incorrect place in a container. Instead we can just pass the values in as command line flags (which is what the files are). We get the values by introducing a go generate step which embeds the flags into a file as a []string.

Additionally this makes it easier to use a our own CTAGS_COMMAND in development.

There are several commits in this PR. Likely easiest to review the final state, and view each commit for context.

My intention is to pull this code out into a shared lib and get Zoekt to use the same library. This should remove inconsistencies between the two environments as well as remove extra requirements on how we build containers.