feat(session-server): add session server for app launching, remove apps from init manifest

Init now only starts servers. The session server holds ProcessCreate cap
and launches apps on demand. Snake is no longer in the boot manifest.

crates/servers/session-server/src/lib.rs

@@ -0,0 +1,8 @@
+#![no_std]
+
+pub mod protocol;
+pub mod server;
+
+#[cfg(test)]
+#[path = "tests/mod.rs"]
+mod tests;