fix: custom network settings form

[alexruzenhack]

Acceptance Criteria

• Should add a scroll for custom network settings form, to avoid overflow of elements in the screen
• Should add a padding to keep the field on screen when the keyboard is open over the field
• Should add form validation for wallet-service fields, to avoid errors on saga processing
  • If any of the wallet-service fields are filled, then all the fields should be filled, otherwise an invalid error should appear in the empty field
  • if all the wallet-service fields are filled, or none are filled, then the form is allowed to be sent

It resolves: https://github.com/HathorNetwork/hathor-wallet-mobile/issues/458

iOS

https://github.com/HathorNetwork/hathor-wallet-mobile/assets/5992210/f861f1a2-e26a-4754-85a3-25c729c60666

Android

custom-network-settings-android.webm

Security Checklist

• [x] Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.