collab: Remove dependency on X11
I'm not sure if this is the best solution (perhaps pulling
`LanguageName` into a separate `language_types` crate would be
better...?) - but it massively reduces build time / dependencies / size
and means that the collab server no longer requires X11 libraries to be
installed.
tl;dr: `telemetry_events` requires the `language` crate, and the
language crate requires a whole ton of extra stuff. Since
telemetry_events only uses `language` for a single type definition
(`LanguageName`, aka `String`), we can cut all of these out by using the
base `String` type (This doesn't seem too terrible, given that all other
telemetry fields are using basic datatypes like String as opposed to
more strongly-typed variants).
FYI the dependency tree for "why does collab need X11 libraries??" looks
like this:
```
collab
\- telemetry_events
\- language
|- gpui
|- fuzzy
| \- gpui
|- git
| \- gpui
|- lsp
| |- gpui
| \- release_channel
| \- gpui
|- settings
| |- fs
| | \- gpui
| \- gpui
|- task
| \- gpui
\- theme
\- gpui
```
Release Notes:
- N/A
This makes it possible to have multiple Dockerfiles, each with their own
`.dockerignore`. Previously any docker builds would always include
anything inside `.dockerignore`. I believe this feature may require
`export DOCKER_BUILDKIT=1` but we use that in CI already.
