[region-isolation] Change semantics of function_extract_isolation from AssertingIfNonSendable -> Require.

The reason why I am doing this is that:

1. function_extract_isolation can take as a parameter a non-Sendable function
today in SIL so in such a case, we crash.
2. It returns an Optional<any Actor> which always must be Sendable.

So it makes sense for it to just require that its non-Sendable parameter not be
transferred at that point.

Author: gottesmm

lib/SILOptimizer/Analysis/RegionAnalysis.cpp

@@ -2638,7 +2638,7 @@ CONSTANT_TRANSLATION(DynamicMethodBranchInst, TerminatorPhi)
 CONSTANT_TRANSLATION(AwaitAsyncContinuationInst, AssertingIfNonSendable)
 CONSTANT_TRANSLATION(GetAsyncContinuationInst, AssertingIfNonSendable)
 CONSTANT_TRANSLATION(ExtractExecutorInst, AssertingIfNonSendable)
-CONSTANT_TRANSLATION(FunctionExtractIsolationInst, AssertingIfNonSendable)
+CONSTANT_TRANSLATION(FunctionExtractIsolationInst, Require)
 
 //===---
 // Existential Box

test/Concurrency/transfernonsendable_instruction_matching.sil

@@ -17,6 +17,7 @@ sil_stage raw
 
 import Swift
 import Builtin
+import _Concurrency
 
 class NonSendableKlass {}
 
@@ -1545,6 +1546,22 @@ bb0(%index : $Builtin.Word):
   return %9999 : $()
 }
 
+sil @function_extract_isolation_test_closure : $@convention(thin) (@guaranteed Optional<any Actor>, Int) -> ()
+
+// This used to crash when function_extract_isolation was AssertingIfNonSendable.
+sil [ossa] @function_extract_isolation_test : $@async @convention(thin) (@owned Optional<any Actor>, Int) -> () {
+bb0(%actor : @owned $Optional<any Actor>, %int : $Int):
+  %f = function_ref @function_extract_isolation_test_closure : $@convention(thin) (@guaranteed Optional<any Actor>, Int) -> ()
+  %closure = partial_apply [isolated_any] [callee_guaranteed] %f(%actor, %int) : $@convention(thin) (@guaranteed Optional<any Actor>, Int) -> ()
+  %closure_b = begin_borrow %closure : $@callee_guaranteed @isolated(any) () -> ()
+  %outputActor = function_extract_isolation %closure_b : $@callee_guaranteed @isolated(any) () -> ()
+  end_borrow %closure_b : $@callee_guaranteed @isolated(any) () -> ()
+  destroy_value %closure : $@callee_guaranteed @isolated(any) () -> ()
+
+  %9999 = tuple ()
+  return %9999 : $()
+}
+
 sil [ossa] @begin_unpaired_access_test : $@async @convention(thin) () -> () {
 bb0:
   %constructFn = function_ref @constructNonSendableKlass : $@convention(thin) () -> @owned NonSendableKlass