[FLINK-8325] Add COUNT AGG support constant parameter, i.e. COUNT(*), COUNT(1) - ASF JIRA

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COUNT(1) with Group Window, always output 0.
e.g.
DATA:

val data = List(
    (1L, 1, "Hi"),
    (2L, 2, "Hello"),
    (4L, 2, "Hello"),
    (8L, 3, "Hello world"),
    (16L, 3, "Hello world"))

SQL:

SELECT b, COUNT(1) FROM MyTable GROUP BY Hop(proctime, interval '0.001' SECOND, interval '0.002' SECOND),b

OUTPUT:

1,0,1, 
1,0,1, 
2,0,1,
2,0,1, 
2,0,2, 
3,0,1,
3,0,1

blocks

FLINK-8355 DataSet Should not union a NULL row for AGG without GROUP BY clause.

links to

GitHub Pull Request #5241