[UR][CUDA][HIP] Allow adapter objects to block full adapter teardown.

[aarongreig]

In the cuda adapter the adapter struct itself is currently an extern global defined in adapter.cpp. This means fully tearing down the adapter is subject to the same destructor ordering as all other static and global variables, it's first in last out. This presents a problem because an application can declare a static sycl object like a buffer right up top before doing anything else, which results in the sycl object being destroyed after the cuda adapter struct.

The UR spec doesn't put the onus on users to keep their parent object lifetimes in order, i.e. there is no statement about "the context you use to create a ur_mem_handle_t must not be released until after the mem_handle". It's assumed (by omission rather than explicitly) that adapters will have their objects keep a reference to any parent objects alive for the duration of their own lifetime.

This change moves the cuda adapter structs ownership into a global shared_ptr, which allows child objects of the adapter to keep their own references to it alive past the point where its initial definition goes out of scope. Also adjusts how some other objects track parent object references so that the destructors correctly cascade back to the top: mem handle releases its context, which releases its adapter, which releases the platform + devices, etc.

All of this also applies to the hip adapter, although it seems something in hip itself prevents this change from fixing the static_buffer_dtor test - see #17571 (comment)

Fixes #17450

[aarongreig]

this is a wider problem with the adapters (and spec to some extent) which I plan to address, but I think it's fine for this to go through as a stand-alone patch for now

[npmiller]

Note that this test is also failing on HIP, I suspect it might require the exact same patch for the HIP adapter

[aarongreig]

I'm just getting a hip environment spun up to see if the fail is indeed this problem as the symptoms in the ticket are slightly different (hang rather than crash)

[aarongreig]

I'm going to push the equivalent hip adapter patch but sadly it doesn't fix the fail. Even with everything on the UR side still alive during the static buffer destructor we get a segfault in libamdhip64.so.6 during this call https://github.com/intel/llvm/blob/sycl/unified-runtime/source/adapters/hip/device.hpp#L116. I tried sticking a hipDeviceGet call in just prior to that and it seems to work fine, but SetDevice still segfaults. I even tried adding a hipInit call there to no effect.

I can only assume that hip itself has some static or otherwise globally managed state that hipSetDevice relies on, as you can imagine there isn't much online about static lifetimes and hip objects

[againull]

sycl changes LGTM