feat: continued bytesbuf tidying

[sandersaares]

Updates API documentation with new and improved terminology. One step of many - further iterations for API docs improvement will follow.

Removes the requirement to go through bytes::Buf and bytes::BufMut traits when performing reads/writes on BytesBuf/BytesView. These traits are still implemented but now there are also equivalent inherent methods (sometimes with better signatures, no longer trying to maintain parity with bytes API signatures).

In a later iteration, the bytes compatibility traits will move behind a feature flag - not fully rooted out yet from all the places.

Removes usage of bytes::Buf and bytes::BufMut from examples, relying on inherent bytesbuf methods only.

Improved panic documentation and assertion logic with regard to some obscure cases like exceeding usize::MAX.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.0%. Comparing base (32e413b) to head (8298a04).
⚠️ Report is 59 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main     #132     +/-   ##
=========================================
  Coverage   100.0%   100.0%             
=========================================
  Files          33       90     +57     
  Lines        3291     6373   +3082     
=========================================
+ Hits         3291     6373   +3082     

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