Un-reject mempool transactions if the rejection depends on the current tip

[teor2345]

Motivation

Some mempool rejections only apply to the current tip, so we want to un-reject them whenever the tip changes.

We also want to make sure the rejection lists don't get too big.

Closes #2694.
Implements part of #2759 (some size limits).

Specifications

The mempool rejection rules aren't really specified anywhere.

We're re-using the size limit from ZIP-401 for all our reject lists:

The size of RecentlyEvicted SHOULD never exceed eviction_memory_entries entries,
which is the constant 40000.

https://zips.z.cash/zip-0401#specification

Solution

• Split mempool storage errors into tip-based and chain-based
• Expire tip rejections every time we get a new block
• Enforce MAX_EVICTION_MEMORY_ENTRIES for mempool reject lists

We might want to wait to add more tests until after PR #2821 or ZIP-401, because the APIs are still changing a lot.

Review

Anyone can review this PR, but I think @conradoplg wants it so he can complete PR #2821.

Reviewer Checklist

• Code implements Specs and Designs
• Tests for Expected Behaviour
• Tests for Errors

[conradoplg]

Rebased and force-pushed after mempool-iter-name-cleanup was merged

[conradoplg]

Looks good!