Allow for in-place update when affinity or spread was changed

[pawelbeza]

Fixes #25070

Similarly to #6732 it removes checking affinity and spread for inplace update.
Both affinity and spread should be as soft preference for Nomad scheduler rather than strict constraint. Therefore modifying them should not trigger job reallocation.

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[tgross]

This looks great @pawelbeza! Thanks!

We've had a discussion internally and have some concerns that folks may be relying on the buggy behavior, even though it wasn't documented either way (Hyrum's Law). So we're going to merge this but hold off on releasing it until the next major version of Nomad (1.10.0 LTS).

I've rebased this PR on main and pushed a commit with some documentation updates. I'll need to pull in another reviewer to merge.

[aimeeu]

Thanks Tim for adding the docs!

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