Deprecate DeviceType in favor of _AcceleratorType

[kaushikb11]

What does this PR do?

Part of #9932

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cc @Borda @justusschock @awaelchli @akihironitta

[awaelchli]

Suggested change

	and trainer._device_type != _AcceleratorType.TPU
	and not isinstance(trainer.accelerator, TPUAccelerator)

Outside of the trainer/accelerator connector, this is how we want to check for the accelerator type in the future. Just a reminder, let's update this in follow up PRs

[kaushikb11]

Yup!

[codecov]

Codecov Report

Merging #10503 (b5fa982) into master (b57fecc) will increase coverage by 0%.
The diff coverage is 94%.

@@           Coverage Diff           @@
##           master   #10503   +/-   ##
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  Coverage      92%      92%           
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  Files         177      177           
  Lines       16404    16411    +7     
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+ Hits        15059    15066    +7     
  Misses       1345     1345