[OMPIRBuilder] - Make offloading input data persist for deferred target tasks.

When we offload to the target, the pointers to data used by the kernel are
passed in arrays created by OMPIRBuilder. These arrays of pointers are allocated
on the stack on the host. This is fine for the most part because absent the `nowait`
clause, the default behavior is that target tasks are included tasks. That is, the
host waits for the target task (in other words, the target kernel) to complete
before proceeding. In turn, this means that the host's stack frame is intact and
accessing the array of pointers when offloading is safe. However, when nowait is
used on the `!$ omp target` instance, then the target task is a deferred task meaning,
the generating task on the host does not have to wait for the target kernel to finish.
In such cases, it is very likely that the stack frame of the function invoking the target
call is wound up thereby leading to memory access errors as shown below.

AMDGPU error: Error in hsa_amd_memory_pool_allocate: HSA_STATUS_ERROR_INVALID_ALLOCATION: The requested allocation is not valid.
AMDGPU error: Error in hsa_amd_memory_pool_allocate: HSA_STATUS_ERROR_INVALID_ALLOCATION: The requested allocation is not valid.
"PluginInterface" error: Failure to allocate device memory: Failed to allocate from memory manager
fort.cod.out: /llvm/llvm-project/offload/plugins-nextgen/common/src/PluginInterface.cpp:1434:
Error llvm::omp::target::plugin::PinnedAllocationMapTy::lockMappedHostBuffer(void *, size_t):
Assertion `HstPtr && "Invalid pointer"' failed.
Aborted (core dumped)

This PR implements support in OMPIRBuilder to store these arrays of pointers in the task structure
that is passed to the target task thereby ensuring it is available to the target task
when the target task is eventually scheduled.

Author: bhandarkar-pranav

llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h

@@ -2496,7 +2496,7 @@ class OpenMPIRBuilder {
       TargetTaskBodyCallbackTy TaskBodyCB, Value *DeviceID, Value *RTLoc,
       OpenMPIRBuilder::InsertPointTy AllocaIP,
       const SmallVector<llvm::OpenMPIRBuilder::DependData> &Dependencies,
-      bool HasNoWait);
+      TargetDataRTArgs &RTArgs, bool HasNoWait);
 
   /// Emit the arguments to be passed to the runtime library based on the
   /// arrays of base pointers, pointers, sizes, map types, and mappers.  If