Update outdated runners in the benchmarks folder (#91126)

This change updates the platform runners in the benchmarks subdir.

I've attempted to replace the entire group with new code as if the project were recreated with flutter create so that they don't become a Frankenstein of minor changes to make it work again, but just plain old generated code that can be replaced and updated in place.

dev/benchmarks/complex_layout/macos/Flutter/Flutter-Release.xcconfig

diff --git a/dev/benchmarks/complex_layout/macos/Flutter/Flutter-Release.xcconfig b/dev/benchmarks/complex_layout/macos/Flutter/Flutter-Release.xcconfig
new file mode 100644
index 0000000..5caa9d1
--- /dev/null
+++ b/dev/benchmarks/complex_layout/macos/Flutter/Flutter-Release.xcconfig
@@ -0,0 +1,2 @@
+#include? "Pods/Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"
+#include "ephemeral/Flutter-Generated.xcconfig"