resampler: Add a find_base_method function.
resampler: Remove the find_implementation function
resampler: Simplify the find_base_method function
resampler: Add a choose_auto_resampler function.

This function returns our preferred resampler if the user choose the
auto (or if he has chosen an unsupported) resampler.
tests: add resampler-bench program

benchmark program to compare runtime of different resampler implementations

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>