feature request: buildx should timeout if node never becomes healthy

[nicks]

Description

Repro steps

1. Create a garbage http server

python3 -m http.server 1234

2. Create a remote driver that talks to the garbage http server.

docker buildx create --name=garbage --driver=remote tcp://localhost:1234 --use

3. Run a build:

docker buildx build .

Expected result

buildx detects the node is broken and eventually times out

Actual result

buildx sends http requests to the garbage server every 3 seconds, forever (or maybe it times out after an hour but i only waited a few minutes)