remoting (#9680)

This PR provides some of the plumbing needed for a "remote" zed
instance.

The way this will work is:
* From zed on your laptop you'll be able to manage a set of dev servers,
each of which is identified by a token.
* You'll run `zed --dev-server-token XXXX` to boot a remotable dev
server.
* From the zed on your laptop you'll be able to open directories and
work on the projects on the remote server (exactly like collaboration
works today).

For now all this PR does is provide the ability for a zed instance to
sign in
using a "dev server token". The next steps will be:
* Adding support to the collaboration protocol to instruct a dev server
to "open" a directory and share it into a channel.
* Adding UI to manage these servers and tokens (manually for now)

Related #5347

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/collab/migrations.sqlite/20221109000000_test_schema.sql

@@ -400,3 +400,11 @@ CREATE TABLE hosted_projects (
 );
 CREATE INDEX idx_hosted_projects_on_channel_id ON hosted_projects (channel_id);
 CREATE UNIQUE INDEX uix_hosted_projects_on_channel_id_and_name ON hosted_projects (channel_id, name) WHERE (deleted_at IS NULL);
+
+CREATE TABLE dev_servers (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    channel_id INTEGER NOT NULL REFERENCES channels(id),
+    name TEXT NOT NULL,
+    hashed_token TEXT NOT NULL
+);
+CREATE INDEX idx_dev_servers_on_channel_id ON dev_servers (channel_id);