Optionally use only pycbf bindings without cbflib or cbflib_adaptbx

[ndevenish]

This is a PR for changes to optionally support using purely python-based bindings to CBFlib and libimg.

• Split out detectorbase tests into their own test
• Skip detectorbase tests if cbflib_adaptbx is not present (Many formats currently initialise CBF detectorbase even if they don't use, and these are tested)

IF using new pycbf:

• Use pure python MarIP detectorbase
• Don't compile or use cbf_read_buffered_file - use pycbf binding instead

Otherwise, everything should work exactly as it did before.

I've run this both with a plain bootstrap and also a bootstrap where I've rm -rf'd cbflib/ and cbflib_adaptbx/ before configuring the build (I don't know how cbflib_adaptbx dependency is normally pulled in, but it doesn't seem to be via a module?).

At the moment, two tests fail - both reading dials_regression/image_examples/SPring8_ADSC_SN916/Xtal17-2phi_3_015.cbf - which is the only image example in the regression tests that resolves to FormatCBFFull - #366 is a WIP example of how we could remove this dependency and read the format directly.

[codecov]

Codecov Report

Merging #368 (4ac5f05) into main (6737862) will decrease coverage by 0.36%.
The diff coverage is 18.24%.

❗ Current head 4ac5f05 differs from pull request most recent head 9a5e81a. Consider uploading reports for the commit 9a5e81a to get more accurate results

@@            Coverage Diff             @@
##             main     #368      +/-   ##
==========================================
- Coverage   66.56%   66.20%   -0.37%     
==========================================
  Files         184      184              
  Lines       16652    16779     +127     
  Branches     2193     2202       +9     
==========================================
+ Hits        11084    11108      +24     
- Misses       5006     5106     +100     
- Partials      562      565       +3     

[ndevenish]

I've just merged in the branch from #366, which means that all tests now pass (excluding the detectorbase-specific tests mentioned above)

[ndevenish]

with 6737862, none of the actively tested formats in the dials_regression image examples otherwise require detectorbase to function, so the caveat is resolved.