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/backend.native/tests/interop/cpp/cppClass.kt

@@ -1,3 +1,5 @@
+@file:OptIn(kotlinx.cinterop.ExperimentalForeignApi::class)
+
 import kotlinx.cinterop.*
 import kotlin.test.*
 
@@ -132,4 +134,4 @@ fun test2() {
 
 	println("x.useContents {iPub} = ${x.useContents {iPub}}" )
 }
-*/
+*/