Revert "Drop useless bitness property from Architecture"

As it turn outs, `Architecture.bitness` leaks to public Gradle API and
we need to deprecate it gracefully.
This reverts commit 79bf2a1f.

native/utils/src/org/jetbrains/kotlin/konan/target/Architecture.kt

@@ -5,12 +5,12 @@
 
 package org.jetbrains.kotlin.konan.target
 
-enum class Architecture {
+enum class Architecture(val bitness: Int) {
-    X64,
+    X64(64),
-    X86,
+    X86(32),
-    ARM64,
+    ARM64(64),
-    ARM32,
+    ARM32(32),
-    MIPS32,
+    MIPS32(32),
-    MIPSEL32,
+    MIPSEL32(32),
-    WASM32;
+    WASM32(32);
 }