Cyclic reference involving class Context

[b-studios]

This PR is a minimalization of an incremental compilation error that we consistently hit, when modifying our Typer.scala.

(reported here: scala/scala3#20245)

Steps to reproduce:

sbt> clean
sbt> compile

Modify a line in Typer.scala

effekt/effekt/shared/src/main/scala/effekt/Typer.scala

Lines 12 to 21 in 34b9e79

	trait TyperOps extends ErrorReporter { self: Context =>
	// passing `this` as ErrorReporter here is also NECESSARY for the cyclic error
	private[typer] val unification = new Unification(using this)
	// this export is NECESSARY for the cyclic error
	export unification.{ requireSubtype }
	// vvvvvvvv insert a line here, save, and run `compile` again vvvvvvvvvv
	}

sbt> compile

Observed result:

[error] -- [E046] Cyclic Error: /private/tmp/effekt/effekt/shared/src/main/scala/effekt/Typer.scala:15:57
[error] 15 |  private[typer] val unification = new Unification(using this)
[error]    |                                                         ^
[error]    |                                Cyclic reference involving class Context
[error]    |
[error]    | longer explanation available when compiling with `-explain`
[error] one error found
[error] (root / Compile / compileIncremental) Compilation failed