[uuid] Replace properties with Final fields

[srittau]

Add UUID.__setattr__

Closes: #14964

[srittau]

psycopg is doing evil things, so I think the primer warning is acceptable:

https://github.com/psycopg/psycopg/blob/bc00e70457f31c48915ea5dce795c60fad57003c/psycopg_c/psycopg_c/_uuid.py#L28

[AlexWaygood]

I understand the motivation of changing UUID.int and UUID.is_safe, since these are not actually properties at runtime and are included in __slots__. But what's the motivation of changing the other properties? Most of these actually are properties at runtime, and are not included in __slots__ (so are unrelated to the issue Eric reported):

>>> from uuid import UUID
>>> UUID.__slots__
('int', 'is_safe', '__weakref__')
>>> UUID.int
<member 'int' of 'UUID' objects>
>>> UUID.is_safe
<member 'is_safe' of 'UUID' objects>
>>> UUID.bytes_le
<property object at 0x1034cb470>
>>> UUID.clock_seq
<property object at 0x1034dc220>

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

psycopg (https://github.com/psycopg/psycopg)
+ psycopg_c/psycopg_c/_uuid.py:28: error: Incompatible types in assignment (expression has type "Callable[[str, Any], None]", base class "UUID" defined the type as "Callable[[object, object], Never]")  [assignment]

[AlexWaygood]

Thanks!