Add unsafeIsolate and extract to std/isolation [backport:1.4] (#17263)

(cherry picked from commit 19be5eb1eb)

changelog.md

@@ -44,5 +44,7 @@
 
 
 
+- Added `unsafeIsolate` and `extract` to `std/isolation`.
+
 ## Tool changes
 

lib/std/isolation.nim

@@ -30,3 +30,11 @@ func isolate*[T](value: sink T): Isolated[T] {.magic: "Isolate".} =
   ## Please read https://github.com/nim-lang/RFCs/issues/244
   ## for more details.
   Isolated[T](value: value)
+
+func unsafeIsolate*[T](value: sink T): Isolated[T] =
+  ## Creates an isolated subgraph from the expression `value`.
+  Isolated[T](value: value)
+
+func extract*[T](src: var Isolated[T]): T =
+  ## Returns the internal value of `src`.
+  result = move(src.value)