feat(jailing): Identify inactivity upon EndBlocker

[gitferry]

This PR (part of #682) is to impelement liveness handler within EndBlocker. Some notable changes:

• Implement algorithm to update the signing info and detect inactive finality providers.
• Add hook AfterFinalityProviderActivated to x/btcstaking and implementation in x/finality to create a signing info when a finality provider is activated. By activated, we mean the finality provider enters the active set for the first time or re-enters the set
• Add inactive flag to the finality provider to indecate whether inactivity of the finality provider is detected
• Add hook AfterInactiveFinalityProviderDetected to x/finality and implementation in x/btcstaking to set the inactive flag of the finality provider to true
• Fuzz test of livenss handler

[gitferry]

One note though, given that inactivity is purely informational flag (without any penalies) which will probably be triggered when fp misses his vote, maybe it makes sense to bring this flag to false after next successful vote instead of having separate message ? This can be done in separate pr though.

@KonradStaniec Good point. For story 1, we don't need to send a separate message to set the inactive to false. But I don't think we should set it to false upon next successful vote. It should also depend on the same detection algorithm. Specifically, we can set it back to false if the missed block counter is below the threshold and the inactive was set to true. Will implement this in a separate PR