Fix sporadic test failures in machinepoollet test suite

[ushabelgur]

Proposed Changes

• As common MachinePool is being used across all controller package testcases, sometime MachineClasses attached to the pool are not yet deleted and we are doing equal comparison of list of resources, which is causing test case to fail sometimes.
• Instead of equal added contains check to see if MachinePool contains newly created MachineClasses with expected quantity

Fixes #1323

[ushabelgur]

I see some other tests failing after fixing machinePoollet related tests
Like this https://github.com/ironcore-dev/ironcore/actions/runs/16320623702/job/46097150773?pr=1330 and
this https://github.com/ironcore-dev/ironcore/actions/runs/16335652712/job/46147139835?pr=1330
Should fix them as well

[Rohit-0505]

I see some other tests failing after fixing machinePoollet related tests Like this https://github.com/ironcore-dev/ironcore/actions/runs/16320623702/job/46097150773?pr=1330 and this https://github.com/ironcore-dev/ironcore/actions/runs/16335652712/job/46147139835?pr=1330 Should fix them as well

You may have a look at this test also
https://github.com/ironcore-dev/ironcore/actions/runs/16337620897/job/46152743268?pr=1333

[ushabelgur]

I see some other tests failing after fixing machinePoollet related tests Like this https://github.com/ironcore-dev/ironcore/actions/runs/16320623702/job/46097150773?pr=1330 and this https://github.com/ironcore-dev/ironcore/actions/runs/16335652712/job/46147139835?pr=1330 Should fix them as well

You may have a look at this test also https://github.com/ironcore-dev/ironcore/actions/runs/16337620897/job/46152743268?pr=1333

@lukas016 can we open separate PR for other sporadic test failures, may be we can close this one