Explicitly declare stability levels of declarations in kotlinx.cinterop package

* @ExperimentalForeignApi for all declarations that operate on
    unmanaged memory (i.e. pointers and references)
* @BetaInteropApi for the rest of the interoperability declarations,
    namely Swift/CInterop-specific interfaces and convenience-functions

### Implementation details

* Some typealiases are not marked explicitly because it crashes the compiler,
    yet their experimentality is properly propagated
* License header is adjusted where it previously had been existing
* Deprecated with ERROR interop declarations that are deprecated for more than
    two years are removed
* WASM target interop declarations are deprecated
* Deliberately make Boolean.toByte and Byte.toBoolean foreign-experimental to scare
    people away

^KT-57728 fixed

Merge-request: KT-MR-9788
Merged-by: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>

kotlin-native/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/StubIrTextEmitter.kt

@@ -4,6 +4,7 @@
  */
 package org.jetbrains.kotlin.native.interop.gen
 
+import kotlinx.cinterop.ExperimentalForeignApi
 import org.jetbrains.kotlin.native.interop.gen.jvm.KotlinPlatform
 import org.jetbrains.kotlin.native.interop.indexer.*
 import org.jetbrains.kotlin.utils.addIfNotNull
@@ -114,6 +115,7 @@ class StubIrTextEmitter(
         }
 
         out("@file:Suppress(${suppress.joinToString { it.quoteAsKotlinLiteral() }})")
+        out("@file:OptIn(ExperimentalForeignApi::class)")
         if (pkgName != "") {
             out("package ${context.validPackageName}")
             out("")