Add support for pg RIGHT/FULL [OUTER] JOIN

[de-luca]

Description

Support for RIGHT and FULL joins would be great to have maximum flexibility without relying on hacks using LEFT JOIN or UNION.

[griffio]

Currently, this is limited by the implementation of JoinClauseMixin in sql-psi project https://github.com/AlecKazakova/sql-psi/blob/6ea26b938a617c74e0b12c782dae9e9a8cc62537/core/src/main/kotlin/com/alecstrong/sql/psi/core/psi/mixins/JoinClauseMixin.kt#L65

The base SQL implementation only supports resolving columns with LEFT joins as not all databases e.g MySql support FULL joins.

🛠️ Changing the PostgreSql grammar is possible, but making a change in sql-psi to allow adding more joins clauses needs some thinking about 🤔

It would be beneficial to allow different vendor joins, as the latest version of Sqlite supports RIGHT and FULL joins. MySql supports RIGHT joins and PostgreSql supports additionally LATERAL.