feat(Inactivity): Add LivenessDelay to finality params and logic for reverting inactive flag

[gitferry]

This PR is part of #682 and a follow-up to https://github.com/babylonchain/babylon/pull/681#discussion_r1658290121. Specifically, this PR:

• Add LivenessDelay to x/finality params, which sepcifies a number of heights after which we examine the liveness of finality providers at a certain height. For example, the current height is 100 and params.LivenessDelay = 3, then we will deal with liveness issues at height 97. This is introduced due to the fact that we allow finality sigs after quorum.
• We revert the inactive flag of a finality provider according to the same algorithm that setting the inactive flag to true. For example, in a signed window of 100, we determine a fp to be inactive if it misses more than 50 blocks. So, if this fp is already inactive, it will be reverted at the height where the missed count is reduced to 50 in the window.

[SebastianElvis]

I don't see any concerns on liveness or impact on reward distribution from my side. Do you have any concerns?

Per yesterday's discussion. maybe we can worry about this later?

[gitferry]

Per yesterday's discussion. maybe we can worry about this later?

Yep, will probably compose a RFC for this. Merging this PR now