[API] Implement Session.undeclare( undeclarable )

[DariusIMP]

Describe the feature

Currently, the Kotlin API allows to undeclare a key expression with session.undeclareKeyExpr(keyExpr).res().

However the Rust API provides a generic undeclare(_undeclarable_) method that receives an element implementing the Undeclarable trait (that is either a subscriber, publisher, queryable or keyexpr).
The Kotlin API should provide a similar functionality.