Add the ability to search or filter the pubkeys in the staking brain list

[JHGrove3]

Is your feature request related to a problem? Please describe.

I'm experimenting with exiting validators on Holesky. I have 16 keys in the staking brain. I had a specific one that I wanted to exit. There was no easy way for me to find it in the list.

Describe the solution you'd like

I would like to be able to paste a pubkey or part of a pubkey in a "search" or "filter" field, and have the list of keys update and only show me the pubkey(s) that matched the text I typed.

Describe alternatives you've considered

The best option I currently have is to sort the pubkeys alphabetically, then scroll through the list until I get to the one I want. But if I had more validators, this would be a real hassle.

Additional context

This will be more important as people run lots of keys for the Lido CSM module

[pablomendezroyo]

@mateumiralles I think this is a great proposal to improve the staking brain UI