media: Add fuzzer test for bit_reader

Also fixes a problem in bit_reader_core where skipping off the end of the buffer doesn't properly updated the bits used, so it appears that some bits are still available but any subsequent operation fails.

TEST=fuzzer test runs locally

Review URL: https://codereview.chromium.org/1754523004

Cr-Commit-Position: refs/heads/master@{#380205}
3 files changed