multi: source index notifs. from block notifs.

[dnldd]

Depends on #2219

This updates the index subscriber to use block notifications as the source of index notifications.

[davecgh]

I'll need to wait until the prequisite PR is finalized and this is rebased and upgraded accordingly before final approval, but I did want to comment that the overall approach seems fine here.

[davecgh]

This will need a rebase after #2219 is merged and is also failing the build.

[davecgh]

I'll need to test this before approving, but the updated version looks good. I don't see any issues code wise and it is much cleaner and more efficient this way.

[matheusd]

Working as intended

[rstaudt2]

This looks good to me other than I noticed that IsTreasuryEnabled is not being set correctly on indexers.IndexNtfn. I noticed this is also the case here in this code that is already merged:

dcrd/blockchain/indexers/common.go

Lines 535 to 541 in ed51788

	ntfn := &IndexNtfn{
	NtfnType: DisconnectNtfn,
	Block: block,
	Parent: parent,
	PrevScripts: prevScripts,
	Done: make(chan bool),
	}

[davecgh]

I'll be testing this with the latest updates tonight.

[davecgh]

Looks good. I tested this by dropping all of the indexes and allowing them to be reindexed from scratch and then performing the various RPCs that make use of said indexes.

[rstaudt2]

Looks good. Are you planning on also updating this location in a separate PR? Just want to make sure we don't forget about that.

[dnldd]

Whoops, good catch @rstaudt2. Missed that, resolving.