During early experiments the logic for "compiling" a configs.Module into
a bunch of configgraph node objects was just a bunch of unexported
functions directly in package eval, because it wasn't clear yet what
abstraction would make most sense between those two.
Now that this has solidified a little more this commit is a first attempt
at drawing a line between packages implementing "compilation" for specific
editions of the language (for which there is currently only one, which
I've named "tofu2024" as a placeholder because Terraform's only existing
language was similarly called "TF2021") and the top-level evaluation
package that tries to be as edition-agnostic as possible, although it is
currently still the one responsible for deciding to call into tofu2024.
There doesn't seem much point in abstracting away the decision about what
edition to use until we actually have a plan to introduce a new edition
and therefore have some idea of what the design constraints for that might
turn out to be.
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
