Expose Backtraces internals from ghc-experimental

Additionally, expose the same API `base:Control.Exception.Backtrace`
to make it easier to use as a drop-in replacement.

(cherry picked from commit 6602472)

Author: fendor

libraries/ghc-experimental/src/GHC/Exception/Backtrace/Experimental.hs

@@ -9,12 +9,20 @@ Portability :  non-portable (GHC extensions)
 
 This module exposes experimental extensions to the Backtrace mechanism of GHC.
 -}
-module GHC.Exception.Backtrace.Experimental (
-  -- * Collecting exception annotations (like backtraces)
-  CollectExceptionAnnotationMechanism,
-  getCollectExceptionAnnotationMechanism,
-  setCollectExceptionAnnotation,
-  collectExceptionAnnotation,
+module GHC.Exception.Backtrace.Experimental
+    ( -- * Backtrace mechanisms
+      BacktraceMechanism(..)
+    , getBacktraceMechanismState
+    , setBacktraceMechanismState
+    -- * Collecting backtraces
+    , Backtraces(..),
+    , displayBacktraces
+    , collectBacktraces
+    -- * Collecting exception annotations on throwing 'Exception's
+    , CollectExceptionAnnotationMechanism
+    , getCollectExceptionAnnotationMechanism
+    , setCollectExceptionAnnotation
+    , collectExceptionAnnotation
   ) where
 
 import GHC.Internal.Exception.Backtrace