For full keymaps, ensure keymap items are lists to allow predictable
manipulation at runtime.
When calling `keymap_init_from_data` directly, allow any sequence type
to allow tools to define their keymaps as tuples.
Ensure we use lists for keymap items and item properties.
This means scripts can access keymap definitions from other layouts,
manipulating them without sometimes encountering a tuple that needs
to be converted into a list.
bpy_extras were meant to be useful high-level helper functions for
script authors to perform common operations,
to avoid writing to verbose API's.
bpy_extras.keymap_utils contains some specialized API calls
mainly intended for Blender's own internal use.
Move keymap import export to internal API.
