Summary:
The name `src` is confusing when combined with the plugins and the newly
added `liboffload`.

Summary:
This patch unifies the existing offloading entires into a single section
called `llvm_offload_entires`. This lets us use a more unified
offloading infrastructure so that all targets share the same handling.
The effect is that people in the runtimes now need to check if the kind
is what they expect, but the expectation is that you can combine
multiple potential providers into a compile job. Doesn't fully work
yet because of other runtime issues, but some day. Mostly this helps the
future of liboffload where we want to handle different languages than
OpenMP.

https://github.com/codespell-project/codespell

% `codespell
--ignore-words-list=archtype,hsa,identty,inout,iself,nd,te,ths,vertexes
--write-changes`

Summary:
The previous offloading entry type did not fit the current use-cases
very well. This widens it and adds a version to prevent further
annoyances. It also includes the kind to better sort who's using it.

The first 64-bytes are reserved as zero so the OpenMP runtime can detect
the old format for binary compatibilitry.

Summary:
This patch is an NFC renaming to make using the offloading entry type
more portable between other targets. Right now this is just moving its
definition to LLVM so others can use it. Future work will rework the
struct layout.

When we use the device, e.g., with an API that interacts with it, we
need to ensure the image is loaded and the constructors are executed.
Two tests are included to verify we 1) load images and run constructors
when needed, and 2) we do so lazily only if the device is actually used.

---------

Co-authored-by: Joseph Huber <huberjn@outlook.com>

The `llvm-omp-device-info` tool is very handy, but broke due to the lazy
evaluation of devices. This repairs the functionality and adds a test.
The tool is also renamed into `llvm-offload-device-info` as `-omp-` is
going away.

Summary:
Currently, we register images into a linear table according to the
logical OpenMP device identifier. We then initialize all of these images
as one block. This logic requires that images are compatible with *all*
devices instead of just the one that it can run on. This prevents us
from running on systems with heterogeneous devices (i.e. image 1 runs on
device 0 image 0 runs on device 1).

This patch reworks the logic by instead making the compatibility check a
per-device query. We then scan every device to see if it's compatible
and do it as they come.

Summary:
There was a bug here where we would initialize the plugin multiple times
when there were multiple images. Fix it by putting the `is_initliaized`
check later.