Move Netgear LTE constants to their own file

[tkdrob]

Breaking change

Proposed change

Preliminary PR as suggested by @epenet before #92632 is to be merged
Move constants to their own file

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[epenet]

This is still a mix of multiple refactoring.
Moving constants should be one PR, moving base entity another, using _attr_has_entity_name and attributes should be again a follow-up.

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[epenet]

These three can be dropped. They are now in const.

[tkdrob]

I think you meant the platforms

[epenet]

LGTM 👍