Properly support categories when benchmarking on Android (#6187)
Properly support categories when benchmarking on Android (#6187)

This avoids hardcoding the "TensorFlow" category. Instead we get
the category from the directory structure. This enables supporting
other categories (e.g., TFLite, MLIR microbenchmarks, etc.) in the
future.

Also clarified various variable names regarding directories and
added typing markers.
iree-org/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,google/iree,iree-org/iree