Apply performance optimizations to `rev-share-limit`

[lightwalker-eth]

The leaderboard is built off of a set of registrar actions.

We don't need to refetch the full set each time we update the leaderboard. Instead, we can apply a performance optimization where:

• registrar actions > X old can safely be considered immutable. This "> X old" check protects against potential chain reorgs.
• We only need to fetch the incremental set of registrar actions and then apply some deduplication logic considering how we would be purposefully overfetching in the rule above.

Happy to share more details via a call 👍