[release-1.28] Fix: Preserve Whitespace for Tag Values Resembling "null" to Prevent ARM Assignment Errors #8121

[nilo19]

This is an automated cherry-pick of #8119

/king bug

Tags with values resembling "null" (e.g., " null " or " NuLL ") will now retain their leading and trailing whitespace during inheritance or updates to avoid errors caused by ARM's reserved tag value "null". 
This change only affects tags with such specific values, ensuring all other tags continue to have whitespace trimmed as before.

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[nilo19]

/retest

[nilo19]

/kind bug

[k8s-ci-robot]

@nilo19: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cloud-provider-azure-e2e-ccm-capz-1-28	b3d0f77	link	true	/test pull-cloud-provider-azure-e2e-ccm-capz-1-28
pull-cloud-provider-azure-e2e-ccm-vmss-multi-slb-capz-1-28	b3d0f77	link	true	/test pull-cloud-provider-azure-e2e-ccm-vmss-multi-slb-capz-1-28
pull-cloud-provider-azure-e2e-ccm-vmss-ip-lb-capz-1-28	b3d0f77	link	true	/test pull-cloud-provider-azure-e2e-ccm-vmss-ip-lb-capz-1-28
pull-cloud-provider-azure-e2e-capz-1-28	b3d0f77	link	true	/test pull-cloud-provider-azure-e2e-capz-1-28
pull-cloud-provider-azure-e2e-ccm-vmss-capz-1-28	b3d0f77	link	true	/test pull-cloud-provider-azure-e2e-ccm-vmss-capz-1-28

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