Elimination of outer joins, if the predicates can restrict the result sets so that all null-supplying rows are eliminated

I found that impala do not have this feature yet when i develop this feature in Apache Doris.

So i want to contribute this feature to impala in the meantime.

Doris issue could be found in this link

The key idea describe below:

Elimination of outer joins, if the predicates can restrict the result sets s
all null-supplying rows are eliminated

• full outer -> inner if both sides have such predicates
• left outer -> inner if the right side has such predicates
• right outer -> inner if the left side has such predicates
• full outer -> left outer if only the left side has such predicates
• full outer -> right outer if only the right side has such predicates