Split cats-effect and fs2 dependencies out of Core

[dylemma]

This is to avoid the dependency hell that is the cats-effect 2.x -> 3.x migration.

The main points:

• Adds the spac-interop-fs2 module to house all of the CE3-friendly stuff like transformer.toPipe and parser.parseF(stream)
• Adds the Source[A] type to Core that's essentially a Resource[Fallible, Iterator[A]] that's friendly for synchronous-style parsing but also can be converted to a Stream[F, A] easily.
• Made it so there are less implicits involved with being able to call .parse on something. All of the *Support imports are gone; instead you explicitly call e.g. JavaxSource.fromFile to get a Source which can be passed to a Parser. The Parsable typeclass is gone.