Make it (a tiny bit) easier to run your own collab (#9557)

* Allow creating channels when seeding
* Allow configuring a custom `SEED_PATH`
* Seed the database when creating/migrating it so you don't need a
  separate step for this.

Release Notes:

- N/A

docs/src/developing_zed__building_zed_linux.md

@@ -16,12 +16,6 @@ git submodule update --init --recursive
   rustup update
   ```
 
-- Install the Rust wasm toolchain:
-
-  ```bash
-  rustup target add wasm32-wasi
-  ```
-
 - Install the necessary system libraries:
 
   ```bash