Ready for review. This should make it easier for people to run a pruned node. If someone starts with -prune core will automatically try to set txindex and disablegovernance to the proper values, and will abort if not possible. It still shows the "governance validation is disabled" message but I made it a bit less scary. In the future I plan on changing it so that that warning will only pop up if it's a users first time in pruned mode, or if they aren't in pruned mode but have governance validation disabled.

Pls see https://github.com/UdjinM6/dash/commits/pr3579:

• 34f5c1508ce17e9c946972165800ccb7a039cb11 is needed to ensure consistency of newly added checks/assignment of -disablegovernance
• 1d0d61df8a4eb87ec498fc636bf95f0f2e755859 is a cleanup, this logic really belongs to AppInitParameterInteraction
• b2bb2649ee2e557adada59b975d620fcfef535bf is needed to fix blockchain.py and it's actually ok to skip this warning on pruned nodes completely, see inline comments
• 57dbd7748670cb0626aaa15f6d07b07cfb806e53 trivial text tweaks

I generally disagree with b2bb2649ee2e557adada59b975d620fcfef535bf because it is still important for pruned node operators to realize that they aren't doing FULL validation, only mostly full validation. I want in the future that warning to only pop up in case of first launch prune or launching w/o prune

Well, then you need smth like 97e0fafcaa for example cause blockchain.py fails because of this warning atm.

done

Hmm... looks like more changes are needed to fix tests, pls see 4e9dfe90bb

commited suggestion

cherry-picked

backported in #3670