[Feature] Extend MaxValueWriter with reduce parameter for the rank_key

[albertbou92]

Description

The current version of the MaxValueWriter only allows to reduce the rank_key by summing along the last dimension.
In a similar fashion to the PrioritizedSampler, this PR introduces a reduce parameter so that users have more control about how the rank_key will be handled when it has more that 1 dimension. Options are: max, min, mean, median and sum.

Motivation and Context

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You can use the syntax close #15213 if this solves the issue #15213

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
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• Example (update in the folder of examples)

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• I have updated the documentation accordingly.

[pytorch-bot]

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✅ You can merge normally! (27 Unrelated Failures)

As of commit 642fff3 with merge base f4878c9 ():

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

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[vmoens]

LGTM! Thanks