Validator manager import to allow `--suggested-fee-recipient` for all keystore files

[chong-he]

In lighthouse vm import, the flag --suggested-fee-recipient currently is only tied to the --keystore-file (the keystore file format created using ethstaker-deposit-cli). So if a user creates the --validators-file using lighthouse vm create and using --suggested-fee-recipient flag during importing, it generates an unclear error message:

error: the following required arguments were not provided:
  --password <STRING>
  --keystore-file <PATH_TO_KEYSTORE_FILE>

Usage: lighthouse validator_manager import --password <STRING> --keystore-file <PATH_TO_KEYSTORE_FILE> --validators-file <PATH_TO_JSON_FILE> --vc-token <PATH> --network <network> --suggested-fee-recipient <ETH1_ADDRESS>

We can remove the .requires line here:

lighthouse/validator_manager/src/import_validators.rs

Line 116 in 999b045

.requires(KEYSTORE_FILE_FLAG),

so that the fee recipient can be set during import for both types of keystore files

Thanks to @anisoptera for highlighting the issue https://discord.com/channels/605577013327167508/938294480279334912/1387583324922449991

Edit: some other flags are also having the same issue, such as builder-boost-factor, builder-proposals