Add a test for remote tool use by the agent (#30289)

- Adds a new smoke test for the use of the read_file tool by the agent
in an SSH project
- Fixes the SSH shutdown sequence to use a timer from the app's executor
instead of always using a real timer
- Changes the main executor loop for tests to advance the clock
automatically instead of panicking with `parked with nothing left to
run` when there is a delayed task

Release Notes:

- N/A

crates/remote_server/Cargo.toml

@@ -69,6 +69,8 @@ fork.workspace = true
 libc.workspace = true
 
 [dev-dependencies]
+assistant_tool.workspace = true
+assistant_tools.workspace = true
 client = { workspace = true, features = ["test-support"] }
 clock = { workspace = true, features = ["test-support"] }
 dap = { workspace = true, features = ["test-support"] }
@@ -79,6 +81,7 @@ language = { workspace = true, features = ["test-support"] }
 node_runtime = { workspace = true, features = ["test-support"] }
 project = { workspace = true, features = ["test-support"] }
 remote = { workspace = true, features = ["test-support"] }
+language_model = { workspace = true, features = ["test-support"] }
 lsp = { workspace = true, features=["test-support"] }
 unindent.workspace = true
 serde_json.workspace = true