[SYCL][Doc] Update KernelProperties extension

[Pennycook]

This commit makes several changes, to align with other extensions and
address feedback and concerns:

• To align with changes to the base property list extension, the _v
  suffix has been dropped from property values.

• The "property_list" class is now called "properties". Some text in the
  extension still refers to the concept of a "property list" because this
  is easier to read.

• Using a member function in conjunction with a tag type prevents kernel
  functors from accidentally implementing the properties interface, and
  prevents naming conflicts with existing variables in user code.

Signed-off-by: John Pennycook john.pennycook@intel.com

[Pennycook]

I'll leave this as a draft until #5338 is merged, but I'd appreciate another pair of eyes on the renaming and feedback on the updated mechanism for embedding properties in a kernel.

[bader]

@Pennycook, do you want me to merge it or wait for a feedback from @rolandschulz?
The same question for #5353.

[Pennycook]

@Pennycook, do you want me to merge it or wait for a feedback from @rolandschulz? The same question for #5353.

Please wait until @steffenlarsen has reviewed #5338 and that's been merged, just in case I need to reflect any changes here.

[steffenlarsen]

Please wait until @steffenlarsen has reviewed #5338 and that's been merged, just in case I need to reflect any changes here.

Sorry! I forgot to hit the approve-button. #5338 should be ready for merge now.

Note that #5338 does not move compile-time property list to the experimental namespace, but there will be another PR shortly after to move it, so the changes here should be correct.

[Pennycook]

Thanks, @steffenlarsen. @bader, this can be merged now.