* test/e2e: replace sleeps with event-driven waits in chaos/group/store tests
Replace 21 time.Sleep calls with deterministic waiting using
WaitForOutput, WaitForTCPReady, and a new WaitForTCPUnreachable helper.
Add CountOutput method for snapshot-based incremental log matching.
* test/e2e: validate interval and cap dial/sleep to remaining deadline in WaitForTCPUnreachable
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.
