Add unit test for streaming aggregator

[yl-lisen]

Describe what enhancement you'd like to have

[juntao-lei-timeplus]

Cover the following streaming aggregation scenarios:

• global append-only input,append-only output aggr
• global append-only input,updates output aggr
• global append-only input,changelog output aggr
• global changelog input,append-only output aggr
• global changelog input,updates output aggr
• global changelog input,changelog output aggr
• window append-only input,append-only output aggr
• window append-only input,updates output aggr