Reactive scopeless (#1341)

Make all reactive builders top-level functions instead of extensions on CoroutineScope and prohibit jobs in their context

Downsides of having lifecycle-managed scoped builders:
  * The lifecycle of semantically cold entity is managed externally by the hot-one.
  * Independent failures in independent triggered computations affect each other
  * Two cancellation sources should be managed, coroutine-related Job parent and disposable/subscription

diff --git a/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-rx2.txt b/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-rx2.txt
index 67ef8a1..54a9663 100644
--- a/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-rx2.txt
+++ b/binary-compatibility-validator/reference-public-api/kotlinx-coroutines-rx2.txt
@@ -21,7 +21,9 @@
 }
 
 public final class kotlinx/coroutines/rx2/RxCompletableKt {
+	public static final fun rxCompletable (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Completable;
 	public static final fun rxCompletable (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Completable;
+	public static synthetic fun rxCompletable$default (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Completable;
 	public static synthetic fun rxCompletable$default (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Completable;
 }
 
@@ -35,17 +37,23 @@
 }
 
 public final class kotlinx/coroutines/rx2/RxFlowableKt {
+	public static final fun rxFlowable (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Flowable;
 	public static final fun rxFlowable (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Flowable;
+	public static synthetic fun rxFlowable$default (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Flowable;
 	public static synthetic fun rxFlowable$default (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Flowable;
 }
 
 public final class kotlinx/coroutines/rx2/RxMaybeKt {
+	public static final fun rxMaybe (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Maybe;
 	public static final fun rxMaybe (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Maybe;
+	public static synthetic fun rxMaybe$default (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Maybe;
 	public static synthetic fun rxMaybe$default (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Maybe;
 }
 
 public final class kotlinx/coroutines/rx2/RxObservableKt {
+	public static final fun rxObservable (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Observable;
 	public static final fun rxObservable (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Observable;
+	public static synthetic fun rxObservable$default (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Observable;
 	public static synthetic fun rxObservable$default (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Observable;
 }
 
@@ -54,7 +62,9 @@
 }
 
 public final class kotlinx/coroutines/rx2/RxSingleKt {
+	public static final fun rxSingle (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Single;
 	public static final fun rxSingle (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;)Lio/reactivex/Single;
+	public static synthetic fun rxSingle$default (Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Single;
 	public static synthetic fun rxSingle$default (Lkotlinx/coroutines/CoroutineScope;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lio/reactivex/Single;
 }