test(tvix/store): 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: I3056b1525784cd712b1d81f84876c9ca0be10dc6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9569
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Tested-by: BuildkiteCI

tvix/Cargo.lock

@@ -2818,6 +2818,7 @@ dependencies = [
  "thiserror",
  "tokio",
  "tokio-listener",
+ "tokio-retry",
  "tokio-stream",
  "tokio-util",
  "tonic",