Moving distinct to Map

[jdunkerley]

Pull Request Description

Changing the implementation of Vector.distinct to be based off the Enso map class.

Initial QA process of the previous implementation highlighted differences in equality comparison in Enso and polyglot functions (HashMap in this case). By moving to a Map based implementation the Enso based equality is used.

It also allows for use of bespoke types which have comparison operators.

Important Notes

• No change to the public API of distinct

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All documentation and configuration conforms to the markdown and YAML style guides.
• All code has been tested where possible.

[farmaazon]

I was just caught as a CHANGELOG owner.