[ownership] Enable GlobalOpt on ossa and add ossa tests (#32621) (#34495)
GlobalOpt works mostly on trivial values (there are special cases for ObjectInst and ValueToBridgeObjectInst).
optimizeGlobalAccess is explicitly turned off for non-trivial values. optimizeInitializer calls SILGlobalVariable::isValidStaticInitializerInst which limits it to mostly trivial values except for special cases for ObjectInst and ValueToBridgeObjectInst.
This changes adds GlobalOpt tests for ossa and enables GlobalOpt on ossa
Co-authored-by: Meghana Gupta <meghanavgupta@gmail.com>