* Fix histogram test
Use different Start index so skipped start_index copy would not get
unnoticed in the test.
* Fix several test_vector_* for valid data
Instead of comparing the moved-from data which is invalid, compare with
the valid initial_data.
* Fix test_vector to check for the correct iterator position after erase
This was done before, but a recent change dropped it.
* Fix bit_stream: Guard nbits > 0 to prevent division by zero
* Cleanup
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Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>