Modify is_execution_policy test to reflect change in specification

[adamfidel]

Closes #1901.

The oneDPL specification has recently changed (uxlfoundation/oneAPI-spec#567) to move is_execution_policy and is_execution_policy_v from the oneapi::dpl::execution namespace to oneapi::dpl. This PR changes the tests to use the struct in the oneapi::dpl namespace for testing.

[danhoeflinger]

I think that this PR is not exactly making the change suggested by the change in the specification. This PR just changes the namespace we are using and then inserts execution inline. I think we need to remove all the inline execution to comply with the "suggestion for new code". However, it probably makes sense to test both oneapi::dpl::execution and oneapi::dpl since both options are available from the specification.

[adamfidel]

I think that this PR is not exactly making the change suggested by the change in the specification. This PR just changes the namespace we are using and then inserts execution inline. I think we need to remove all the inline execution to comply with the "suggestion for new code". However, it probably makes sense to test both oneapi::dpl::execution and oneapi::dpl since both options are available from the specification.

The PR is only inserting execution:: prefixes for the execution policies themselves and not for the two type traits that have moved out of that namespace (is_execution_policy and is_execution_policy_v). We still need execution:: for the policies because they are still in the execution namespace whereas the utility structs are now not.

Although I agree that it probably makes sense to test both oneapi::dpl:: and oneapi::dpl::execution:: versions of the utility structs. Let me see how I can easily do that in the same test file.

[danhoeflinger]

The PR is only inserting execution:: prefixes for the execution policies themselves and not for the two type traits that have moved out of that namespace (is_execution_policy and is_execution_policy_v). We still need execution:: for the policies because they are still in the execution namespace whereas the utility structs are now not.

Although I agree that it probably makes sense to test both oneapi::dpl:: and oneapi::dpl::execution:: versions of the utility structs. Let me see how I can easily do that in the same test file.

Oh whoops yes my mistake. My brain short circuited and made a bad assumption. Sorry about that.

It is probably enough to have a small check of the execution namespace just that they are present, perhaps not a full copy of the test again for both namespaces.

[danhoeflinger]

I think this mostly LGTM after some small test of presence of the traits directly in the execution namespace too.

[adamfidel]

I think this mostly LGTM after some small test of presence of the traits directly in the execution namespace too.

I restructured the test a bit and it now checks for the traits in both the oneapi::dpl and the oneapi::dpl::execution namespaces.

I believe this newer version simplifies the code which results in a smaller set of changes.

[danhoeflinger]

I restructured the test a bit and it now checks for the traits in both the oneapi::dpl and the oneapi::dpl::execution namespaces.

I believe this newer version simplifies the code which results in a smaller set of changes.

Yes I like this much better, let me take a closer look but on first inspection it looks good.

[danhoeflinger]

LGTM, pending green CI

[danhoeflinger]

optional nitpick, this could be constexpr.