Python: Add class validation for Dapr Runtime step loading #10244

Job	Run time
Python Unit Tests (3.11, ubuntu-latest, false)	2m 39s
Python Unit Tests (3.10, windows-latest, false)	3m 50s
Python Unit Tests (3.12, macos-latest, false)	2m 15s
Python Unit Tests (3.10, macos-latest, false)	3m 10s
Python Unit Tests (3.13, ubuntu-latest, true)	5m 10s
Python Unit Tests (3.10, ubuntu-latest, false)	2m 27s
Python Unit Tests (3.11, windows-latest, false)	4m 18s
Python Unit Tests (3.11, macos-latest, false)	4m 8s
Python Unit Tests (3.12, windows-latest, false)	4m 13s
Python Unit Tests (3.12, ubuntu-latest, false)	2m 35s
	34m 45s

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