[Node operation] Allow private keys to loaded from a different directory than the genesis data

[vishalchangrani]

Instructions

Reported by Anchorage

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Issue To Be Solved

Currently, a Flow node expects a bootstrap directory where it finds the private keys and the genesis data both. The private keys cannot be kept separate than the genesis data in a different folder. The Flow node should allow for specifying the private keys and genesis data folder separately to allow for easier key management.

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(Optional): Context

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