The empty value in the query result needs to be filled

[xiangyu5632]

Is your feature request related to a problem? Please describe.（如果该特性或者功能和已知某个问题相关，请描述问题是什么）

In the case of non-grouped aggregation, the empty value in the query result needs to be filled. The filling policy includes the filling of the specified value, previous value, and next value.

> select f1,f2 from tab
name: tab
time                f1  f2
----                --  --
1708309973145615335 1   2
1708309982273595148     2
1708498828793592694 111 
1708498857079672776     22
1708498877520925921 11  22
1708498890752021155     23
1708498899049189513 12 

need
1. Gaven a value to fill in

> select f1,f2 from tab fill(50)
name: tab
time                f1  f2
----                --  --
1708309973145615335 1   2
1708309982273595148 50  2
1708498828793592694 111 50
1708498857079672776 50  22
1708498877520925921 11  22
1708498890752021155 50  23
1708498899049189513 12  50

2. Use the previous value to fill in

> select f1,f2 from tab fill(previous)
name: tab
time                f1  f2
----                --  --
1708309973145615335 1   2
1708309982273595148 1   2
1708498828793592694 111 2
1708498857079672776 111 22
1708498877520925921 11  22
1708498890752021155 11  23
1708498899049189513 12  23
>