I just panicked and wanted to see the cause, but forgot that panic files
get deleted when Zed uploads them.
Release Notes:
- Panics are now written to `~/Library/Logs/Zed/Zed.log`
Before (code in screenshot is from this branch,
`crates/zed/languages/rust.rs:179`):

Notice how the last 2 entries (that are async functions) are not
highlighted properly.
After:

This is slightly suboptimal, as it's hard to tell that this is an async
function - I guess adding an `async` prefix is not really an option, as
then we should have a prefix for non-async functions too. Still, at
least you can tell that something is a function in the first place. :)
Release Notes:
- Fixed Rust async functions not being highlighted in completions.
The goal of this PR is to make Following more intuitive.
### Old Behavior
Previously, following was scoped to a project. In order to follow
someone in a given window, the window needed to contain a shared
project, and the leader needed to be present in the project. Otherwise,
following failed.
### New Behavior
* You can always follow **any** participant in the current call, in any
pane of any window.
* When following someone in a project that you're both collaborating in,
it works the same as before.
* When following someone in an unshared project, or a project that they
don't have open, you'll only get updates about the leader's views that
don't belong to a project, such as channel notes views. When the leader
focuses a file in a different project, you'll get the "follow $LEADER to
their active project" indicator
### Todo
* [x] Change db schema and RPC protocol so a project id isn't required
for following
* [x] Change client to allow following into non-project items regardless
of the leader's project
* [x] Assign colors to users in a way that doesn't require users to be
in a shared project.