[JS IR] Add annotation for eager property initialization

compiler/testData/codegen/box/properties/eagerInitializationGlobal1.kt

@@ -0,0 +1,27 @@
+// TARGET_BACKEND: JS_IR
+// DONT_TARGET_EXACT_BACKEND: WASM
+// PROPERTY_LAZY_INITIALIZATION
+
+// FILE: lib.kt
+var z1 = false
+var z2 = false
+
+// FILE: lib2.kt
+
+@OptIn(kotlin.ExperimentalStdlibApi::class)
+@JsEagerInitialization
+val x = foo()
+
+private fun foo(): Int {
+    z1 = true
+    return 42
+}
+
+// Will be initialized since [x]'s initializer calls a function from the file.
+val y = run { z2 = true; 117 }
+
+// FILE: main.kt
+
+fun box(): String {
+    return return if (z1 && z2) "OK" else "fail"
+}

compiler/testData/codegen/box/properties/eagerInitializationGlobal2.kt

@@ -0,0 +1,22 @@
+// TARGET_BACKEND: JS_IR
+// DONT_TARGET_EXACT_BACKEND: WASM
+// PROPERTY_LAZY_INITIALIZATION
+
+// FILE: lib.kt
+var z1 = false
+var z2 = false
+
+// FILE: lib2.kt
+
+@OptIn(kotlin.ExperimentalStdlibApi::class)
+@JsEagerInitialization
+val x = run { z1 = true; 42 }
+
+// Won't be initialized (cause no function from the file will be called during [x] initialization).
+val y = run { z2 = true; 117 }
+
+// FILE: main.kt
+
+fun box(): String {
+    return if (z1 && !z2) "OK" else "fail"
+}