audio: Fix some issues stemming from the recent re-org

[jepler]

• consistently use audiosample_mark_deinit
• remove unused functions and their prototypes, such as common_hal_audioio_rawsample_get_sample_rate(audioio_rawsample_obj_t *self);

These notes stem from my review of #10052

[jepler]

The missing use of mark_deinit is probably going to be causing some bugs, like the ability to use a sample after it was deinitialized, in some contexts.