[#1181] Correct computation of progress for Spend before Sync

- the computation of progress changed, the total range is computed, that way it works for any kind of sync algorithm
- the progress depends on finished scan action, whenever it processes some blocks, it's counted up
- the final progress is a ratio between these new values

Example/ZcashLightClientSample/ZcashLightClientSample/DemoAppConfig.swift

@@ -30,7 +30,7 @@ enum DemoAppConfig {
     static let defaultSeed = try! Mnemonic.deterministicSeedBytes(from: """
     kitchen renew wide common vague fold vacuum tilt amazing pear square gossip jewel month tree shock scan alpha just spot fluid toilet view dinner
     """)
-    
+
     static let otherSynchronizers: [SynchronizerInitData] = [
         SynchronizerInitData(
             alias: .custom("alt-sync-1"),

Sources/ZcashLightClientKit/Block/Actions/ProcessSuggestedScanRangesAction.swift

@@ -46,7 +46,7 @@ extension ProcessSuggestedScanRangesAction: Action {
             await context.update(lastScannedHeight: lowerBound)
             await context.update(lastDownloadedHeight: lowerBound)
             await context.update(syncControlData: syncControlData)
-            
+
             // the total progress range is computed only for the first time
             // as a sum of all ranges
             let totalProgressRange = await context.totalProgressRange