Started implementation for more clear stage-1 intermediate form.

Removed stupid `klvm-trap-error` from deinline-expr. It should emit correct
KLambda now. Cleaned reg-kl naming (also reg-kl -> regkl).
Stage-1 intermediate form is useful for unifying compilation to KLVM and
bytecode:

Shen -> KLambda -> RegKLambda -> KLVM.Stage1 -> KLVM
                                             -> bytecode