add L1 support to getCurrentValidators API

[ceyonur]

Why this should be merged

It adds L1 support and shows L1 validators in platform.getCurrentValidators API.

How this works

• Added validationID to the platform.getL1Validator API.
• Added L1 support to the platform.getCurrentValidators API.
• Removed the PermissionedValidator struct as it is no longer used.
• Introduced getL1Validators and getPrimaryOrSubnetValidators methods to handle fetching validators based on subnet ID.
• Added convertL1ValidatorToAPI method to convert L1 validator data to API format.
• Added GetL1Validators method to the State interface to return both base stakers and L1 validators in a converted L1.

How this was tested

Locally

Need to be documented in RELEASES.md?

Yes, updated.