Replicated Security soft opt-out

[mpoke]

Problem

The current design of Replicated Security requires all validators to validate on all consumer chains.

Closing criteria

Soft opt-out is enabled -- allow the bottom x% of the validator set by power to opt out of validating consumer chains without being jailed or otherwise punished for it.

Task list

Must have

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1. Soft opt-out #765
   type: feature-request type: protocol-change +2
   
2. ADR for soft opt-out #1000
   scope: docs +1
   

Nice to have

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1. Soft opt-out threshold is hardcoded #893
   good first issue question type: tech-debt +3
   
2. Soft opt out - finish testing #849
   scope: testing +1
   
3. test soft opt-out with diff testing #1044
   S: Productivity scope: testing +2