Refix dtype in aggregation metrics

[SkafteNicki]

What does this PR do?

Fixes #2365

Original PR #2366 did actually not fix the problem because I used torch.allclose in the comparison of results instead of hard equal ==. This PR rectify this by making sure we never convert to lower precision internally in the aggregation metrics (using the dtype property from #2379).

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

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📚 Documentation preview 📚: https://torchmetrics--2386.org.readthedocs.build/en/2386/

[codecov]

Codecov Report

Merging #2386 (050a8c7) into master (442c463) will not change coverage.
The diff coverage is 20%.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2386   +/-   ##
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  Coverage      69%     69%           
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  Files         307     307           
  Lines       17351   17351           
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  Hits        11960   11960           
  Misses       5391    5391