Fix YAMLDecoder Read behaviour

[sel]

What this PR does / why we need it:

Makes YAMLDecoder adhere to the Read contract by returning the number of bytes
read.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #56999

Special notes for your reviewer:

Release note:

YAMLDecoder Read now returns the number of bytes read

[sel]

/assign @deads2k

[danielqsj]

/lgtm

[k8s-ci-robot]

@danielqsj: changing LGTM is restricted to assignees, and only kubernetes org members may be assigned issues.

In response to this:

/lgtm

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[dims]

/ok-to-test

[sel]

The test failure seems unrelated to this change (segfault in the JVM while building the docs)
/retest

[sel]

/retest

[sel]

Thanks for the review, @mikedanese.
PTAL and let me know if I should squash the commits.

[mikedanese]

/lgtm

[sel]

/test pull-kubernetes-e2e-gce

[deads2k]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: danielqsj, deads2k, mikedanese, sel

Associated issue: #56999

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these OWNERS Files:

• staging/src/k8s.io/apimachinery/pkg/OWNERS [deads2k]

You can indicate your approval by writing /approve in a comment
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[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 57324, 56931, 57000, 57150, 56965). If you want to cherry-pick this change to another branch, please follow the instructions here.