Reorder top-level elements in file; no code changes.
Reorder top-level elements in file; no code changes.

This change aims to clarify the breadth/scope of inputs.py (especially when the
file is viewed in outline), and can help with future refactoring of trax.data
code. The new order of elements is based on the following:

  - Most-used, most-combinable functions (camel-case names) first; within
    these, preference to most general functions.
  - Other public functions (snake-case names) next; within these, preference to
    gin-configurable functions.
  - Nonpublic functions (not related to Inputs class) next.
  - Inputs class -- to be deprecated eventually -- and associated functions last.

PiperOrigin-RevId: 371188516

google/trax,google/trax