Add stress test for time based key generation

[konradkonrad]

This is the test that uncovered #121 on shutter-api.

On the keyper side a load of 100 time based triggers did not lead to problems:

2026/06/11 12:37:23.240656 INF [    messaging.go:399] sending message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" topic=decryptionKeys
2026/06/11 12:37:23.537000 INF [    messaging.go:399] sending message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" topic=decryptionKeys
2026/06/11 12:37:23.708714 INF [    messaging.go:399] sending message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" topic=decryptionKeys
2026/06/11 12:37:23.801561 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWRPmN8EgxhUEGG5HrRurwxgTFpLyJCFFavqbN7ypu6Ygk topic=decryptionKeys
2026/06/11 12:37:23.848130 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWE6c5jYUBbd39QsL1mNzbSWHCfkhn1VRgk5r2phYWSRw8 topic=decryptionKeys
2026/06/11 12:37:23.893476 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWRPmN8EgxhUEGG5HrRurwxgTFpLyJCFFavqbN7ypu6Ygk topic=decryptionKeys
2026/06/11 12:37:23.935387 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWCiKhTnGjKAwLfc8F6WtWw3ujRYnmxJt3CSP1HyHUENA1 topic=decryptionKeys
2026/06/11 12:37:23.969371 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWE6c5jYUBbd39QsL1mNzbSWHCfkhn1VRgk5r2phYWSRw8 topic=decryptionKeys
2026/06/11 12:37:24.009482 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWG9ywnHhvsk31ubaLYczvxyf9gviPU4bi77hsg5fN5yhN topic=decryptionKeys
2026/06/11 12:37:24.047110 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWG9ywnHhvsk31ubaLYczvxyf9gviPU4bi77hsg5fN5yhN topic=decryptionKeys
2026/06/11 12:37:24.081273 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWCiKhTnGjKAwLfc8F6WtWw3ujRYnmxJt3CSP1HyHUENA1 topic=decryptionKeys
2026/06/11 12:37:24.111849 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWRPmN8EgxhUEGG5HrRurwxgTFpLyJCFFavqbN7ypu6Ygk topic=decryptionKeys
2026/06/11 12:37:24.151644 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWCiKhTnGjKAwLfc8F6WtWw3ujRYnmxJt3CSP1HyHUENA1 topic=decryptionKeys
2026/06/11 12:37:24.188627 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWG9ywnHhvsk31ubaLYczvxyf9gviPU4bi77hsg5fN5yhN topic=decryptionKeys
2026/06/11 12:37:24.218928 INF [    messaging.go:375] received message message="DecryptionKeys{firstIdentity=0x009093b71f06274d914054b4817fe0a261475407f010c0b915fb674df0d4c033, numKeys=100}" sender-id=12D3KooWE6c5jYUBbd39QsL1mNzbSWHCfkhn1VRgk5r2phYWSRw8 topic=decryptionKeys

It is still notable though, to see that one single keyper sent three instances of the DecryptionKeys{firstIdentity=0x009093b71f0-message.

This is a follow up to shutter-network/rolling-shutter#715 -- the goal is to ensure, that no similar bottleneck exists for time based decryption.