Add integration tests for inplace machine upgrade

[aaronfern]

What this PR does / why we need it:
This PR adds integration tests for machine inplace upgrade

The following scenarios have been added

• Happy path - move machine to new mcs after successful upgrade
• Machine transition to InPlaceUpdateFailed phase when node update fails and update-result=failed annotation is set
• Machine transitions to InPlaceUpdateFailed when update result is not set within timeout
• Manual inPlace upgrade

Which issue(s) this PR fixes:
Fixes partially #1123

Special notes for your reviewer:

Release note:

Added integration tests for inPlace machine upgrade

[gardener-prow]

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