Adapt Extension to Exasol v8

[kaklakariada]

The findInstances command reads the virtual schema table SYS.EXA_ALL_VIRTUAL_SCHEMAS. The schema of this table changes in Exasol v8, so we need to adapt the query to also work with Exasol 8.

Precondition: Exasol Docker DB v8 is available that allows running Java UDFs. Without this we can't run integration tests.