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>

generators/nativeInteropRuntime/NativeInteropRuntimeGenerator.kt

@@ -31,6 +31,7 @@ fun FileWriter.generateAllocWithValue(type: PrimitiveInteropType) {
          * Allocates variable with given value type and initializes it with given value.
          */
         @Suppress("FINAL_UPPER_BOUND")
+        @ExperimentalForeignApi
         public fun <T : $typeName> NativePlacement.alloc(value: T): ${typeName}VarOf<T> =
                 alloc<${typeName}VarOf<T>> { this.value = value }
     """.trimIndent()