[mlir-cpu-runner] Support parsing operations other than 'builtin.module' as top-level

This adds a `--no-implicit-module` option, which disables the insertion
of a top-level `builtin.module` during parsing. The top-level op is
required to have the `SymbolTable` trait.

The majority of the change here is removing `ModuleOp` from interfaces.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D134238