Push Down Filter Subexpressions in Nested Loop Joins as Projections (apache#17906)

* Check-in NestedLoopJoinProjectionPushDown

* Update Cargo.lock

* Add some comments

* Update slts that are affected by the nl-join-projection-push-down

* please lints

* Move code into projection_pushdown.rs

* Remove explicit coalesce batches

* Docs

Author: tobixdev

Cargo.lock

@@ -52,5 +52,6 @@ recursive = { workspace = true, optional = true }
 
 [dev-dependencies]
 datafusion-expr = { workspace = true }
+datafusion-functions = { workspace = true }
 insta = { workspace = true }
 tokio = { workspace = true }