Summary:
This was not using the size previously queried and would fail when the
implementation actually verified it.

This is a tool similar to urinfo that simply prints properties of all
devices. The old openMP version has been ported to liboffload.

The order entries in the tablegen API files are iterated is not the
order
they appear in the file. To avoid any issues with the order changing
in future, we now generate all definitions of a certain class before
class that can use them.

This is a NFC; the definitions don't actually change, just the order
they exist in in the OffloadAPI.h header.

Add the following properties in Offload device info:
* VENDOR_ID
* NUM_COMPUTE_UNITS
* [SINGLE|DOUBLE|HALF]_FP_CONFIG
* NATIVE_VECTOR_WIDTH_[CHAR|SHORT|INT|LONG|FLOAT|DOUBLE|HALF]
* MAX_CLOCK_FREQUENCY
* MEMORY_CLOCK_RATE
* ADDRESS_BITS
* MAX_MEM_ALLOC_SIZE
* GLOBAL_MEM_SIZE

Add a bitfield option to enumerators, allowing the values to be
bit-shifted instead of incremented. Generate the per-type enums using
`foreach` to reduce code duplication.

Use macros in unit test definitions to reduce code duplication.

libc++ headers must be generated before compiling part of liboffload. 
The build error occurs if clang is configured to use libc++ by default. 
Fixes issue #149324

When `EnumRec::isTyped()` is true, include the
`EnumValueRec::getTaggedType()` to the documentation.

Add two new symbol info types for getting the bounds of a global
variable. As well as a number of tests for reading/writing to it.

* Add spec generation to offload-tblgen tool
* This patch adds generation of Sphinx compatible reStructuedText
utilizing the C domain to document the Offload API directly from the
spec definition `.td` files.
* Add Sphinx HTML documentation target
* Introduces the `docs-offload-html` target when CMake is configured
with `LLVM_ENABLE_SPHINX=ON` and `SPHINX_OUTPUT_HTML=ON`. Utilized
`offload-tblgen -gen-spen` to generate Offload API specification docs.