Rewrite of the scheduling logic following the addition of Ingest V2.

The logic is isolated from the actor.

This PR still misses several refinement:
- introduce locality in the optimization algorithm
- split the list of shards into several pipelines if necessary.
- add an actual cost function and a BFS.

.gitignore

@@ -8,6 +8,9 @@ local/**
 quickwit/quickwit-ui/package-lock.json
 **/.DS_Store
 
+TODO.md
+QUESTIONS.txt
+
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html