search: New old search implementation (#39956)

This is an in-progress work on changing how task scheduler affects
performance of project search. Instead of relying on tasks being
executed at a discretion of the task scheduler, we want to experiment
with having a set of "agents" that prioritize driving in-progress
project search matches to completion over pushing the whole thing to
completion. This should hopefully significantly improve throughput &
latency of project search.

Release Notes:

- Improved project search performance

---------

Co-authored-by: Smit Barmase <smit@zed.dev>
Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>

crates/project_benchmarks/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "project_benchmarks"
+version = "0.1.0"
+publish.workspace = true
+edition.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+clap.workspace = true
+client.workspace = true
+futures.workspace = true
+gpui = { workspace = true, features = ["windows-manifest"] }
+http_client = { workspace = true, features = ["test-support"]}
+language.workspace = true
+node_runtime.workspace = true
+project.workspace = true
+settings.workspace = true
+watch.workspace = true
+
+[lints]
+workspace = true