* [IRGen] Handle complex single payload enum cases
rdar://110138498
Handles single payload enum cases with more complex bit patterns (e.g. >64 bits or scattered) by storing a relative pointer to a function that reads the tag.
* Use proper symbol for enum tag helper
rdar://109787818
Templatized and abstracted handling of layout strings to simplify future specializations. E.g. specilizing for a particular number of reference count operations can be done by passing the expected size as a template param:
```
extern "C" void
swift_generic_destroy_2(swift::OpaqueValue *address, const Metadata *metadata) {
handleRefCounts<2, DestroyHandler>(metadata, (uint8_t *)address);
}
```
rdar://109790722
Layout strings are not guaranteed to be properly aligned, so we can't directly read from and write to it, but have to use memcpy instead.
* [IRGen] Support additional single payload enum cases in layout strings
rdar://105837101
Adds layout string support for single payload enums with simple (non-scattered) extra inhabitant patterns
* Add more test cases
* [IRGen] Make pointers to accessor functions in layout strings relative
rdar://106319336
Pointers embedded in static layout strings should always be relative, so layout strings can reside in read-only memory.
* Properly handle reference storage ownership
* Pass layout tag and metadata / type layout ppointers separately
* Layout string instantiation fully working
* Fix cases where hasLayoutString flag was not set when it should have
* Update include/swift/ABI/Metadata.h
* [IRGen] Add layout strings for generic and resilient types
rdar://105837048
* Add some corner cases
* Add flag to enable generic instantiation and some fixes
* Fix resilient types
* Fix metadata accessor function pointers in combined layout strings
