Return tuple instead of list from device and platform collection APIs

[vlad-perevezentsev]

Initially the goal was to change dpctl.get_devices() to return a tuple instead of a list to align with the Python Array API specification where info.devices is defined as a tuple

While implementing this change it became clear that the same behavior should be applied consistently across other APIs that return collections of devices or platforms.
This PR also updates get_platforms, get_composite_devices, SyclContext.get_devices, SyclPlatform.get_devices, SyclPlatform.get_composite_devices, SyclDevice.create_sub_devices, SyclDevice.component_devices, and SyclDevice.sub_group_sizes to return tuples instead of lists

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[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/2322/index.html

[coveralls]

coverage: 75.39%. remained the same — use_return_tuple into master

[ndgrigorian]

while we're at it, can we adjust the other docstrings to use the Tuple[:class:] return format? It's a bit more readable

[ndgrigorian]

other than that small adjustment lgtm