Update HIP-631 document with some virftual address stuff that was removed from HIP-632

[david-bakin-sl]

We revised HIP-632 to reflect the reality that HIP-631 isn't implemented (and isn't going to be in the near term). That involved removing some stuff w.r.t. virtual addresses from HIP-632. That stuff should be now added into HIP-631.

(This issue is to track that activity going on over there in the HIP repo - that repo doesn't support issues.)

[Nana-EC]

Also move HIP 631 to Withdrawn given hashgraph/hedera-improvement-proposal#1082