feat(cli): support Prysm keystores

[merklefruit]

Describe the feature

bolt pubkeys local-keystore and bolt delegate local-keystore commands don't currently support Prysm keystores.
We should add support for them as part of our push to increase client compatibility.

Additional context

No response

[0ex-d]

Preamble:

# current command
bolt pubkeys local-keystore --path test_data/lighthouse/validators
# or
bolt pubkeys local-keystore --path test_data/prysm/direct

1. we could accommodate by checking heuristics like pubkey not available in prysm but looks hacky or
2. change to below to specifically load keystores based on CL clients.

# proposed
bolt pubkeys local-keystore --client prysm --path test_data/prysm/direct 

The current implementation (lighthouse client only), loads keystores from bolt-cli/test_data/lighthouse/validators/0x8a../voting-keystore.json.

To implement prysm for example in bolt-cli/test_data/prysm/direct/accounts/all-accounts.keystore.json I believe there has to be a way to distinguish what keystore is being used because of the a few differences in the json data structure.

Let me know what you think.

[0ex-d]

@merklefruit can you please weigh in on this?