This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19521 | core#19521]] [6 & 7/17]
https://github.com/bitcoin/bitcoin/pull/19521/commits/3f166ecc125fce6ccd995687fa16572090a5d099
https://github.com/bitcoin/bitcoin/pull/19521/commits/6a4c0c09ab4d073a26c3c4a02783d5dcd88f6eef (removal of 'disk_size' and 'transactions' from the index and test the RPC on specific heights)
Notes:
- in the source commits there is a call to `::ChainstateActive().ForceFlushStateToDisk();` added, but it is removed in a following commit in the same PR. This is obviously duplicated with the `active_chainstate.ForceFlushStateToDisk()` a few lines later, so I omitted it.
- I added a mention about `disk_size` not being available when using the index in the doc of the RPC call. This is added later in the same PR in an unrelated commit in the source material.
Depends on D11599