Implement combine with context in new spark runner

Validates runner tests below fail in spark structured streaming runner because combine with context (for side inputs) is not implemented:
'org.apache.beam.sdk.transforms.CombineFnsTest.testComposedCombineWithContext''org.apache.beam.sdk.transforms.CombineTest$CombineWithContextTests.testSimpleCombineWithContext''org.apache.beam.sdk.transforms.CombineTest$CombineWithContextTests.testSimpleCombineWithContextEmpty''org.apache.beam.sdk.transforms.CombineTest$WindowingTests.testFixedWindowsCombineWithContext''org.apache.beam.sdk.transforms.CombineTest$WindowingTests.testSessionsCombineWithContext''org.apache.beam.sdk.transforms.CombineTest$WindowingTests.testSlidingWindowsCombineWithContext'