test(tvix/castore): use tokio-retry for exp backoff

Rather than using this loop, use exponential backoff while waiting for
the socket path to be created.

Change-Id: I18706a64ce06f8916a07892dfbcd409ac5b3bff1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9568
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/Cargo.lock

@@ -2460,6 +2460,17 @@ dependencies = [
  "syn 2.0.16",
 ]
 
+[[package]]
+name = "tokio-retry"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f57eb36ecbe0fc510036adff84824dd3c24bb781e21bfa67b69d556aa85214f"
+dependencies = [
+ "pin-project",
+ "rand",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-stream"
 version = "0.1.14"
@@ -2700,6 +2711,7 @@ dependencies = [
  "test-case",
  "thiserror",
  "tokio",
+ "tokio-retry",
  "tokio-stream",
  "tokio-util",
  "tonic",