[OpenMP][MLIR] Descriptor explicit member map lowering changes

This is one of 3 PRs in a PR stack that aims to add support for explicit mapping of
allocatable members in derived types.

The primary changes in this PR are the OpenMPToLLVMIRTranslation.cpp changes,
which are small and seek to alter the current member mapping to add an
additional map insertion for pointers. Effectively, if the member is a pointer
(currently indicated by having a varPtrPtr field) we add an additional map for
the pointer and then alter the subsequent mapping of the member (the data)
to utilise the member rather than the parents base pointer. This appears to be
necessary in certain cases when mapping pointer data within record types to
avoid segfaulting on device (due to incorrect data mapping). In general this
record type mapping may be simplifiable in the future.

There are also additions of tests which should help to showcase the affect
of the changes above.

Pull Request: llvm#96265

mlir/test/Target/LLVMIR/omptarget-fortran-allocatable-types-host.mlir

@@ -61,7 +61,7 @@ module attributes {omp.is_target_device = false, omp.target_triples = ["amdgcn-a
 // CHECK: @[[FULL_ARR_GLOB:.*]] = internal global { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]] } undef
 // CHECK: @[[ARR_SECT_GLOB:.*]] = internal global { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]] } undef
 // CHECK: @.offload_sizes = private unnamed_addr constant [12 x i64] [i64 0, i64 48, i64 8, i64 0, i64 0, i64 48, i64 8, i64 0, i64 0, i64 24, i64 8, i64 4]
-// CHECK: @.offload_maptypes = private unnamed_addr constant [12 x i64] [i64 32, i64 281474976710659, i64 281474976710659, i64 281474976710675, i64 32, i64 1407374883553283, i64 1407374883553283, i64 1407374883553299, i64 32, i64 2533274790395907, i64 2533274790395907, i64 2533274790395923]
+// CHECK: @.offload_maptypes = private unnamed_addr constant [12 x i64] [i64 32, i64 281474976710657, i64 281474976710659, i64 281474976710675, i64 32, i64 1407374883553281, i64 1407374883553283, i64 1407374883553299, i64 32, i64 2533274790395905, i64 2533274790395907, i64 2533274790395923]
 // CHECK: @.offload_mapnames = private constant [12 x ptr] [ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}, ptr @{{.*}}]
 
 // CHECK: define void @_QQmain()