Is your feature request related to a problem or specific use case? Please describe.
ERCE generates keys for each test to use unique keys for enrollments. A new feature to save all these keys to file would be very helpful to use for testing against a new PKI. For example if you want to stress test 10 million certificates having keys saved from previous generation would greatly speed up the tests because the keys would already be present to then stress test 10 million enrollments.

Describe the solution you'd like
Save generated keys to a directory and be able to use a directory full of keys for stress testing.

Describe alternatives you've considered
Getting more compute to generate keys faster, but not everyone has that luxery.

Product deployment
Please complete the following information:
N/A

Additional context
N/A