fix: non-active validators can't verify evidence signatures

[lklimek]

Issue being fixed or feature implemented

Nodes that are not active validators don't have access to public keys of validators, so they cannot verify signatures in evidence.

What was done?

1. Non-validators don't verify signatures
2. Non-validators don't add evidence to evidence pool, to avoid adding fake evidence

How Has This Been Tested?

GHA

Breaking Changes

None

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[shumkov]

👍