Fix https://github.com/llvm/llvm-project/issues/156679

There is a mismatch between the preprocessor guards around the include
of `hwloc.h` and those protecting its usages, leading to build failures
on Darwin: https://github.com/spack/spack-packages/pull/1212

This change introduces `KMP_HWLOC_ENABLED` that reflects
whether hwloc is actually used.

The feature was introduced back in 2014 and has been on ever since.
Leave the feature in place. Removing only the macro.

When running the `openmp` testsuite on Solaris/amd64, many tests `FAIL`
like

```
# | OMP: Error #11: Stack overflow detected for OpenMP thread #1
```

In a `Debug` build, I also get
```
# | Assertion failure at kmp_runtime.cpp(203): __kmp_gtid_get_specific() < 0 || __kmp_gtid_get_specific() == i.
```

Further investigation shows that just setting `__kmp_gtid_mode` to 3
massively reduces the number of failures.

Tested on `amd64-pc-solaris2.11` and `x86_64-pc-linux-gnu`.

TR11 introduced changes to support target memory management in a unified
way by defining a series of API routines and additional traits. Host
runtime is oblivious to how actual memory resources are mapped when
using the new API routines, so it can only support how the composed
memory space is maintained, and the offload backend must handle which
memory resources are actually used to allocate memory from the memory
space.

Here is summary of the implementation.
* Implemented 12 API routines to get/mainpulate memory space/allocator.
* Memory space composed with a list of devices has a state with resource
description, and runtime is responsible for maintaining the allocated
memory space objects.
* Defined interface with offload runtime to access memory resource list,
and to redirect calls to omp_alloc/omp_free since it requires
backend-specific information.
* Value of omp_default_mem_space changed from 0 to 99, and
omp_null_mem_space took the value 0 as defined in the language.
* New allocator traits were introduced, but how to use them is up to the
offload backend.
* Added basic tests for the new API routines.

This patch adds support for memory allocation using hwloc. To enable
memory allocation using hwloc, env KMP_TOPOLOGY_METHOD=hwloc needs to be
used. If hwloc is not supported/available, allocation will fallback to
default path.

Updating OpenMP runtime taskgraph support(record/replay mechanism):

- Adds a `graph_reset` bit in `kmp_taskgraph_flags_t` to discard
existing TDG records.
- Switches from a strict index-based TDG ID/IDX to a more flexible
integer-based, which can be any integer (e.g. hashed).
- Adds helper functions like `__kmp_find_tdg`, `__kmp_alloc_tdg`, and
`__kmp_free_tdg` to manage TDGs by their IDs.

These changes pave the way for the integration of OpenMP taskgraph (spec
6.0). Taskgraphs are still recorded in an array with a lookup efficiency
reduced to O(n), where n ≤ `__kmp_max_tdgs`. This can be optimized by
moving the TDGs to a hashtable, making lookups more efficient. The
provided helper routines facilitate easier future optimizations.