lntest/itest: add itest for SCB file restore for anchor commitments

In this commit, we extend the current SCB recovery tests to also cover
the new anchor commitment type. We only add a single test that covers
the most common case to avoid needing to tests all cases for all
commitment types which is being done in a follow up PR.

lncfg/protocol_legacy_on.go

@@ -19,7 +19,7 @@ type ProtocolOptions struct {
 
 	// Anchors should be set if we want to support opening or accepting
 	// channels having the anchor commitment type.
-	Anchors bool `long:"anchors" description:"EXPERIMENTAL: enable experimental support for anchor commitments. Won't work with watchtowers or static channel backups"`
+	Anchors bool `long:"anchors" description:"EXPERIMENTAL: enable experimental support for anchor commitments, won't work with watchtowers"`
 }
 
 // LegacyOnion returns true if the old legacy onion format should be used when