[SYCL][Doc] Adjust queue priority revision 2 to the implementation
Changes to the moved revision 2 text and the reasons for them:
- Add priority::get_priority(). Without a getter the value of the
property can't be read back with queue::get_property, and other
properties with data, such as compute_index, provide one.
- Document the priority constructor and get_priority in separate member
blocks, as other extension documents do.
- Add a "Conflicting priorities" section. Revision 1 forbids combining
the pre-defined priorities, but revision 2 doesn't specify combining
them with the numeric priority. Extend the existing errc::invalid rule
to all priority properties.
- Allow priority_low to be lower than the lowest priority reported by
priority_range, with a note. Some devices, such as Level Zero GPUs,
support a low priority that has no numeric equivalent, and the
implementation keeps using it for priority_low.
- State that the priority range always contains the default priority 0.
Otherwise priority(0) and priority_normal could be clamped to a
non-default priority.
- Specify that devices without numeric priorities return {0, 0}, so that
priority_range can be queried on any device and clamping to it is
consistent with the default priority.
- Mention in the status note that numeric priorities are only used by
the Level Zero v2 adapter.
- Drop "additional" from the overview, since the document now describes
all properties, and "with fixed numeric values", which doesn't hold
for priority_low and priority_high whose values depend on the device.
Assisted-By: Claude
