Support nullable columns on Right Join and Full Join

[griffio]

To enable a fix in sqldelight/sqldelight#5136

Tested locally and in SqlDelight using snapshot build

For unit testing in sql-psi, the sql.bnf grammar would have to include right and full joins - however, not all databases dialects support full joins, sqlite recently added right joins. Actual tests would have to be added to SqlDelight with a supporting grammar such as Postgresql.

Implementation

💇‍♂️ The existing code present in queryExposed is worked around rather than a complete re-write

🤐 Uses zipWithNext to create a pair of table queries, if there are joins present in the query. These joins could be inner joins or outer joins. Only outer joins are copied with the nullable field set to true.

👥 From each pair, when there is a right or full join the first query columns are copied with nullability, any left or full join nullability columns are produced on the second query columns

This produces duplicate QueryResult columns and
queryAvailable.associateBy { it.table }.values is used to remove the duplicate columns

SELECT A.*, B.*
FROM A LEFT JOIN B USING (id);

LEFT JOINS nulls on right expected and does so in table data interface

id	val1	val2
1	a	null
2	b	null

SELECT A.*, B.*
FROM A RIGHT JOIN B USING (id);

RIGHT JOINS nulls on left side expected and does have nullable types for A fields

id	val1	val2
11	null	a
21	null	b

SELECT A.*, B.*
FROM A FULL JOIN B USING (id);

FULL JOINS nulls on both sides expected and does have nullable types for A, B fields

id	val1	val2
1	a	null
2	b	null
11	null	a
21	null	b

[AlecKazakova]

thank you!