Refactor source layout

Introduce compat source sets and move all kotlin sources to the main directory

[no changelog]

src/main/kotlin/util/Timer.kt

@@ -0,0 +1,25 @@
+
+
+package moe.nea.firmament.util
+
+import kotlin.time.Duration
+import kotlin.time.ExperimentalTime
+import kotlin.time.TimeSource
+
+@OptIn(ExperimentalTime::class)
+class Timer {
+    private var mark: TimeSource.Monotonic.ValueTimeMark? = null
+
+    fun timePassed(): Duration {
+        return mark?.elapsedNow() ?: Duration.INFINITE
+    }
+
+    fun markNow() {
+        mark = TimeSource.Monotonic.markNow()
+    }
+
+    fun markFarPast() {
+        mark = null
+    }
+
+}