Create flag for bypassing startup cryptographic key generations

The startup process currently generates cryptographic keys as part of node initialization [here](https://github.com/hiero-ledger/hiero-consensus-node/blob/6d004de6b4688d8c528803965db6161c0ff0c2e4/hedera-node/hedera-app/src/main/java/com/hedera/node/app/ServicesMain.java#L345-L345). effectively making debugging infeasible due to the processing time taken.

Implement a bypass flag that enables startup from a known set of predefined keys, without spending the processing time to generate said keys.