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ARROW-13878: [C++] Implement fixed-size-binary support for several kernels

All kernels listed in the JIRA, plus casting fixed_size_binary to other binary types, are now supported:

- binary_length
- binary_replace_slice
- count_substring
- find_substring
- find_substring_regex
- equal
- greater
- greater_equal
- less
- less_equal
- fixed_size_binary cast to (large_)binary/utf8
- fixed_size_binary cast to fixed_size_binary
  Note that while CanCast for mismatched widths returns true, the kernel will error during execution still.

Closes #11230 from lidavidm/arrow-13878

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>