Improved key generation with factory pattern

[DanielBoye]

Fixes a TODO in the code:

eigensdk-go/cmd/egnkey/generate.go

Line 76 in a5629b0

// TODO: This can be improved further with a factory pattern

Motivation

Updating to a factory pattern is smart to decouple object creation from its usage in our key generation logic. This change addresses the challenge of supporting multiple key types (ECDSA and BLS) in a scalable way.

Solution

The first I did was to include a KeyGenerator interface and two concrete implementations for ECDSA and BLS key types. The factory function, NewKeyGenerator, dynamically selects the appropriate generator based on input parameters, simplifying the generate function.

Open questions

Would someone mind if we wrote unit tests for the newly implemented factory pattern in our key generation system, particularly focusing on the dynamic selection logic of the NewKeyGenerator function and ensuring each key generator (ECDSA and BLS) behaves as expected under various input conditions? Since as for now the egnkey does not have any test cases.

[samlaf]

@shrimalmadhur can you take a look at this? I believe you wrote the egnkey util?