switch to signed-first approach

It turns out signed math is more performant

src/commonTest/kotlin/com/infendro/bytes/intarray/Conversion.kt

@@ -0,0 +1,61 @@
+package com.infendro.bytes.intarray
+
+import com.infendro.bytes.ByteOrder.LITTLE_ENDIAN
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+
+class IntArrayConversionTest {
+    @Test
+    fun toByteArray() {
+        val expected = arrayOf(
+            byteArrayOf(
+                0x12, 0x34, 0x56, 0x78,
+                0x12, 0x34, 0x56, 0x78,
+            ),
+            byteArrayOf(
+                0x78, 0x56, 0x34, 0x12,
+                0x78, 0x56, 0x34, 0x12,
+            ),
+        )
+        val actual = arrayOf(
+            intArrayOf(
+                0x12345678,
+                0x12345678,
+            ).toByteArray(),
+            intArrayOf(
+                0x12345678,
+                0x12345678,
+            ).toByteArray(LITTLE_ENDIAN),
+        )
+        for (i in 0..1) {
+            assertContentEquals(expected[i], actual[i])
+        }
+    }
+
+    @Test
+    fun toUByteArray() {
+        val expected = arrayOf(
+            ubyteArrayOf(
+                0x12U, 0x34U, 0x56U, 0x78U,
+                0x12U, 0x34U, 0x56U, 0x78U,
+            ),
+            ubyteArrayOf(
+                0x78U, 0x56U, 0x34U, 0x12U,
+                0x78U, 0x56U, 0x34U, 0x12U,
+            ),
+        )
+        val actual = arrayOf(
+            intArrayOf(
+                0x12345678,
+                0x12345678,
+            ).toUByteArray(),
+            intArrayOf(
+                0x12345678,
+                0x12345678,
+            ).toUByteArray(LITTLE_ENDIAN),
+        )
+        for (i in 0..1) {
+            assertContentEquals(expected[i], actual[i])
+        }
+    }
+}