```
The mempool quadratic stats themselves will soon be removed in a future commit.
However, we are removing them from RPC now in this commit to keep things
manageable.
This commit removes the following stats from RPC:
- "ancestor", "descendant", "descendantcount", "descendantsize", "descendantfees",
"ancestorcount", "ancestorsize", "ancestorfees"
- RPC's affected: `getrawmempool true`, `getmempoolancestors`,
`getmempooldescendants`, `getmempoolentry`
```
Port of bchn#1129.
Depends on D13133 and DD13136.
Instead of removing the fields, we deprecate them for backward compatibility.
The mempool_packages.py and mempool_updatefromblock.py tests are kept
unchanged with the deprecation option so we are still testing the feature.
It's also easier than adding the cases to the deprecated RPCs functional test.