[ModuleInterface] Extract the Swift 6 variant from imports.swift

This allows us to limit the test to asserts compiler supporting
-swift-version 6.

rdar://115578753

Author: xymus

test/ModuleInterface/imports-swift6.swift

@@ -0,0 +1,36 @@
+/// Swift 6 variant to imports.swift. Both can be reintegrated once
+/// -swift-version 6 is accepted by release compilers.
+// REQUIRES: asserts
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -emit-module -o %t/empty.swiftmodule %S/../Inputs/empty.swift
+// RUN: %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -emit-module -o %t/emptyButWithLibraryEvolution.swiftmodule %S/../Inputs/empty.swift -enable-library-evolution
+
+/// Swift 6 variant.
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s %S/Inputs/imports-other.swift -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -I %S/Inputs/imports-clang-modules/ -I %t -verify -swift-version 6
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -I %S/Inputs/imports-clang-modules/ -I %t
+// RUN: %FileCheck -implicit-check-not BAD -check-prefix CHECK-6 %s < %t.swiftinterface
+
+@_exported import empty // expected-warning {{module 'empty' was not compiled with library evolution support; using it means binary compatibility for 'main' can't be guaranteed}}
+@_exported import emptyButWithLibraryEvolution
+import B.B2
+import func C.c // expected-warning {{scoped imports are not yet supported in module interfaces}}
+import D
+@_implementationOnly import Secret_BAD
+
+@_implementationOnly import NotSoSecret // expected-note {{imported as implementation-only here}}
+import NotSoSecret2 // expected-warning {{'NotSoSecret2' inconsistently imported as implementation-only}}
+
+// CHECK-6-NOT: import
+// CHECK-6: {{^}}public import A{{$}}
+// CHECK-6-NEXT: {{^}}public import B{{$}}
+// CHECK-6-NEXT: {{^}}public import B.B2{{$}}
+// CHECK-6-NEXT: {{^}}public import B.B3{{$}}
+// CHECK-6-NEXT: {{^}}public import C/*.c*/{{$}}
+// CHECK-6-NEXT: {{^}}public import D{{$}}
+// CHECK-6-NEXT: {{^}}public import NotSoSecret{{$}}
+// CHECK-6-NEXT: {{^}}public import NotSoSecret2{{$}}
+// CHECK-6-NEXT: {{^}}public import Swift{{$}}
+// CHECK-6-NEXT: {{^}}@_exported public import empty{{$}}
+// CHECK-6-NEXT: {{^}}@_exported public import emptyButWithLibraryEvolution{{$}}
+// CHECK-6-NOT: import

test/ModuleInterface/imports.swift

@@ -5,11 +5,6 @@
 // RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -I %S/Inputs/imports-clang-modules/ -I %t
 // RUN: %FileCheck -implicit-check-not BAD %s < %t.swiftinterface
 
-/// Swift 6 variant.
-// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s %S/Inputs/imports-other.swift -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -I %S/Inputs/imports-clang-modules/ -I %t -verify -swift-version 6
-// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -I %S/Inputs/imports-clang-modules/ -I %t
-// RUN: %FileCheck -implicit-check-not BAD -check-prefix CHECK-6 %s < %t.swiftinterface
-
 @_exported import empty // expected-warning {{module 'empty' was not compiled with library evolution support; using it means binary compatibility for 'imports' can't be guaranteed}}
 @_exported import emptyButWithLibraryEvolution
 import B.B2
@@ -33,17 +28,3 @@ import NotSoSecret2 // expected-warning {{'NotSoSecret2' inconsistently imported
 // CHECK-NEXT: {{^}}@_exported import empty{{$}}
 // CHECK-NEXT: {{^}}@_exported import emptyButWithLibraryEvolution{{$}}
 // CHECK-NOT: import
-
-// CHECK-6-NOT: import
-// CHECK-6: {{^}}public import A{{$}}
-// CHECK-6-NEXT: {{^}}public import B{{$}}
-// CHECK-6-NEXT: {{^}}public import B.B2{{$}}
-// CHECK-6-NEXT: {{^}}public import B.B3{{$}}
-// CHECK-6-NEXT: {{^}}public import C/*.c*/{{$}}
-// CHECK-6-NEXT: {{^}}public import D{{$}}
-// CHECK-6-NEXT: {{^}}public import NotSoSecret{{$}}
-// CHECK-6-NEXT: {{^}}public import NotSoSecret2{{$}}
-// CHECK-6-NEXT: {{^}}public import Swift{{$}}
-// CHECK-6-NEXT: {{^}}@_exported public import empty{{$}}
-// CHECK-6-NEXT: {{^}}@_exported public import emptyButWithLibraryEvolution{{$}}
-// CHECK-6-NOT: import