language_models: Count Google AI tokens through LLM service (#29319)

This PR wires the counting of Google AI tokens back up.

It now goes through the LLM service instead of collab's RPC.

Still only available for Zed staff.

Release Notes:

- N/A

Cargo.lock

@@ -18536,9 +18536,9 @@ dependencies = [
 
 [[package]]
 name = "zed_llm_client"
-version = "0.7.0"
+version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3c1666cd923c5eb4635f3743e69c6920d0ed71f29b26920616a5d220607df7c4"
+checksum = "cc9ec491b7112cb8c2fba3c17d9a349d8ab695fb1a4ef6c5c4b9fd8d7aa975c1"
 dependencies = [
  "anyhow",
  "serde",