SI-8219 Coherency for `{Any, Object}#==`; typer.context / infer.context

- Make our ficticious == and != methods line up for overriding checks
  - Eliminate a major source of puzzling behaviour by ensuring Inferencer
    and Typer agree on what the current Context is.

Review by @adriaanm, @xeno-by @lrytz (or any number of people that have been puzzled about what a strange Context was doing in their inferencer over the years...)

These changes are independent, I can break them up if desired. The `==` parts are probably a touch riskier as I don't know the history of the divergent signatures.