Changes from 2.14.4 to 2.15.0

• Removed some duplicated functions. See #503.

• Added a new io mode to memory map files. This forced to change the io_cb read API.
  See https://github.com/Blosc/c-blosc2/blob/main/tests/test_mmap.c to see an example on
  how to use it.

• Updated the SOVERSION to 4 due to the API change in io_cb read.

• Added functions to get cparams, dparams, storage and io defaults respectively.

• Internal zstd sources updated to 1.5.6.

• Fixed a bug when setting a slice using prefilters.