[*] Redesigned datum entry into mempool: now they are recorded with the key...

Backport task #7169 Redesigned datum entry into mempool: now they are recorded with the key not as a datum hash, but as a hash of its contents.

assigned to @roman.khlopkov

added 3 commits

• abdca8da...6a63442c - 2 commits from branch develop
• aa19d55a - Merge remote-tracking branch 'origin/develop' into backport-7169

Compare with previous version

mentioned in commit 05198943

merged