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GH-34636: [C#] Reduce allocations when using ArrayPool (#39166)

### Rationale for this change

GH-34636 is a great suggestion for simplifying the code and making it more efficient by changing the delegate-based RentReturn pattern to a "using"-based one. As most of the affected call sites were the ones not passing CancellationToken properly, it was a good time to fix that as well.

### Are these changes tested?

This is basically a refactoring which doesn't add new functionality and so is covered by existing tests.

Closes #39144
* Closes: #34636

Authored-by: Curt Hagenlocher <curt@hagenlocher.org>
Signed-off-by: Curt Hagenlocher <curt@hagenlocher.org>