ExecutionEngine: provide utils for running CLI-configured LLVM passes

A recent change introduced a possibility to run LLVM IR transformation during
JIT-compilation in the ExecutionEngine.  Provide helper functions that
construct IR transformers given either clang-style optimization levels or a
list passes to run.  The latter wraps the LLVM command line option parser to
parse strings rather than actual command line arguments.  As a result, we can
run either of

    mlir-cpu-runner -O3 input.mlir
    mlir-cpu-runner -some-mlir-pass -llvm-opts="-llvm-pass -other-llvm-pass"

to combine different transformations.  The transformer builder functions are
provided as a separate library that depends on LLVM pass libraries unlike the
main execution engine library.  The library can be used for integrating MLIR
execution engine into external frameworks.

PiperOrigin-RevId: 234173493