Rollup merge of #147952 - ferrocene:pvdrz/remote-test-client-timeout, r=Enselic

Add a timeout to the `remote-test-client` connection

Currently, the `remote-test-client` doesn't have a timeout when connecting to the `remote-test-server`. This means that running tests using it can hang indefinitely which causes issues when running tests on CI, for example.

This PR now sets a default timeout of 5 minutes, meaning that if, for example, `TEST_DEVICE_ADDR=<IP:PORT> ./x test --target riscv64gc-unknown-linux-gnu tests/ui` is run and the `remote-test-server` is not reachable by the client, the client will panic after the timeout is reached.

Additionally, the `TEST_DEVICE_CONNECT_TIMEOUT` env variable can be used to set up the timeout to any value (in seconds).

This PR also wires up a test step for `remote-test-client`, which didn't previously have tool tests run in CI.

Edit: ~~blocked by rust-lang/rust#149071~~

Author: matthiaskrgr

src/tests/running.md

@@ -321,6 +321,10 @@ Tests are built on the machine running `x` not on the remote machine.
 Tests which fail to build unexpectedly (or `ui` tests producing incorrect build
 output) may fail without ever running on the remote machine.
 
+There is a default timeout of 30 minutes in case the `remote-test-server`
+cannot be reached by the `x` command. This timeout can be modified by using the
+`TEST_DEVICE_CONNECT_TIMEOUT_SECONDS` environment variable.
+
 ## Testing on emulators
 
 Some platforms are tested via an emulator for architectures that aren't readily available.