fixes #5773

Exception when using SqlDelight Plugin with PostgreSql Dialect statements CREATE INDEX or CREATE VIEW

Stuck in Analyzing state - means that annotation errors won't get displayed

java.lang.ClassCastException: Don't use #getElementType method. It is deprecated. 
Implement and use #getIElementType ...

Add SchemaContribStub constructor and add copy of ElementType class as sql-psi has internal visibility for existing SqlSchemaContributorElementType

Tested locally now shows green tick or any annotation errors are detected - some way to add test?

Further testing - sometimes I get error in Intellij - need to check new class CreateIndexElementType

java.lang.Throwable: All stub element types should be created before index initialization is complete.
Please add the class app.cash.sqldelight.dialects.postgresql.grammar.mixins.CreateIndexElementType with external ID sqldelight.null containing stub element type constants to "stubElementTypeHolder" extension.
Registered extensions: [com.intellij.util.xml.stubs.DomElementTypeHolder, ...

• Uses sql-psi fix Change visibility for inheritance sql-psi#683

• CHANGELOG.md's "Unreleased" section has been updated, if applicable.