kube: fix quantityToInt64 dropping scale for fractional BinarySI

[guillermodotn]

Replace AsDec().Unscaled() with Quantity.Value() in quantityToInt64(), which properly handles the decimal scale. Remove the now-unused error returns from quantityToInt64 and setupContainerResources. Add unit tests for fractional BinarySI inputs.

Fixes: #28789

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Does this PR introduce a user-facing change?

Fixed `podman kube play` setting incorrect memory limits for fractional BinarySI quantities (e.g. `1.5Gi`).

[TomSweeneyRedHat]

From a quick look, the changes look good. But it looks like you didn't sign your PR, and we can't merge until you do. git commit --amend -s should take care of it, with a fetch, rebase, and push. Thanks!

[danishprakash]

Overall looks good but could you also add an integration test? thanks

[guillermodotn]

Overall looks good but could you also add an integration test? thanks

Added an integration test in test/e2e/play_kube_test.go. That said, I think the unit test alone is sufficient here. The bug is entirely in quantityToInt64(), a function that the unit test covers with the exact inputs that trigger the issue.

[Luap99]

LGTM

[danishprakash]

LGTM (have rerun what seemed to be unrelated failures)