Instead of sending a message to the index log when an indexing task finishes, stream results as they come in

This also means that you can use the index log to view which tasks are currently being executed.

Since we only have a single log stream we can write to, I decided to prefix every line in the index log with two colored emojis that an easy visual association of every log line to the task that generated them.

Sources/SKCore/CompilationDatabaseBuildSystem.swift

@@ -129,7 +129,7 @@ extension CompilationDatabaseBuildSystem: BuildSystem {
 
   public func prepare(
     targets: [ConfiguredTarget],
-    indexProcessDidProduceResult: @Sendable (IndexProcessResult) -> Void
+    logMessageToIndexLog: @Sendable (_ taskID: IndexTaskID, _ message: String) -> Void
   ) async throws {
     throw PrepareNotSupportedError()
   }