SPIRVGlobalRegistry should not be owned by the subtarget

SPIRVGlobalRegistry is owned by the subtarget, and created in the SPIRVSubtarget constructor. The global registry depends on program state, so this is inappropriate. The subtarget is a universal constant that cannot depend on specific IR. A single TargetMachine may be reused for multiple compiles with the same constant TargetSubtargetInfo instances.

This also makes the constructor dependent on TargetMachine::createDataLayout to pass to the constructor.

This needs to be moved somewhere else, like a proper Module analysis pass

Start by tracing SPIRVGlobalRegistry creation in the SPIRVSubtarget constructor and the TargetMachine::createDataLayout dependency. Review how a Module analysis pass could own program-specific state while TargetSubtargetInfo remains reusable across compilations. Done means the registry is no longer owned by the subtarget and the constructor no longer requires this data-layout setup.

Written by the indexing model from the issue text.