30c6c3a0bf
A_burst_of_cold_compiles_does_not_starve_the_heartbeat (50 ms heartbeat) and A_caller_that_blocks_after_its_result_does_not_starve_the_reader (100 ms) launched their worker under the tight silence kill, so its cold start (launch, first compile, Roslyn JIT) had to stay within 150/300 ms of silence. Under 28 busy processes on 14 cores that failed 2 in 10 runs in the WARM-UP, killed for ~165 ms of silence, and replacement workers were killed the same way. New test seam: WorkerLaunchSpec.HeartbeatSilenceLimit (runner internal ctor heartbeatSilenceLimit) and WorkerConnection.SilenceLimit. The tests launch with a 30 s limit, warm, then tighten to three intervals for the phase they are about; the assertions on that phase are unchanged.