Pallet anchors: Evict anchors redesign

[lemunozm]

Description

The current evict_anchor method performs a clean over an unbounded list of elements. Also, the whole evict_anchor process has too much complexity, which can lead to future bugs and reduce its maintainability.

By redesigning this part of the pallet, we could improve both security and maintainability.

How will this affect the code base

• Improve security in the long term.
• Reduce code complexity.

What are foreseen obstacles or hurdles to overcome?

• Migration is needed after the required refactorization.

[lemunozm]

Currently, pallet-anchors benchmarks don't find some hashes in the benchmarks, increasing the measured weights. This is not a security issue, but we are adding more weight than is needed. We need to take this into account for the redesign