[Flang][Tool][bbc] Emit module wrapper in addition to body

This change seeks to emit the full module from the bbc tool and
not just the body. This change currently does not break existing tests
when running check-(mlir, flang, all). This stops the discarding of
any attributes that may be applied to the Module during
compilation.

Reviewed By: jeanPerier
Differential Revision: https://reviews.llvm.org/D144869