Rework the component unit tests to use the managedResourceObjectsMatcher

[ialidzhikov]

How to categorize this PR?

/area testing
/area dev-productivity
/kind enhancement

What this PR does / why we need it:
The managedResourceObjectsMatcher is introduced with gardener/gardener#9964 in gardener/[email protected]. We had an item in our backlog to evaluate it and potentially start using it.
The managedResourceObjectsMatcher:

• reduces some boilerplate - we no longer need to fetch the ManagedResource Secret, then uncompress and decode it to fetch the manifest inside
• we can pass native go types for the expected resources instead of serialized YAML manifests. The YAML manifests are sensitive to whitespace and key order.

Which issue(s) this PR fixes:
N/A

Special notes for your reviewer:
N/A

Release note:

NONE

[dimitar-kostadinov]

/lgtm

[gardener-prow]

LGTM label has been added.

Git tree hash: d72acde0e2082c3017769d4b1c46e34fad246476

[gardener-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dimitar-kostadinov

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