Move crates under substreams directory.

This way we can run GHA jobs depending on what files changed.

substreams/crates/tycho-substreams/src/lib.rs

@@ -0,0 +1,9 @@
+pub mod balances;
+pub mod contract;
+mod mock_store;
+pub mod models;
+mod pb;
+
+pub mod prelude {
+    pub use super::models::*;
+}