Replace the fixed 500ms sleep after each frps startup in RunProcesses
with a TCP dial-based readiness check that polls the server bind port.
This reduces the e2e suite wall time from ~97s to ~43s.
Also simplify the RunProcesses API to accept a single server template
string instead of a slice, matching how every call site uses it.
* add close proxy op
* Move to actual closing routine
* Fix e2e tests for CloseProxy
* Add warning on resource exhaustion
* Add CloseProxy to manual close
* retuen errors to `CloseProxy` callers