Add random axes in full tomo seq

Based on the sequence from ID16A.

• The rand axes field name was changed to be meaningful (i.e. it's not just randomization, it's also following specific axis modelization)
• step_runner stores this metadata in the resulting HDF5
• step_runner has the axis with displacement in axis unit
• fulltomo has the axis with displacement in detector pixel
• Added a test to check processing and the resulting data

What have changed:

Previously at ID16A:

# yml
- class: FullFieldTomo
  rand_mot1: $test_fulltomo_rand_spy
  rand_mot2: $test_fulltomo_rand_spz

# python
fast_scan.pars.disp_mot1 = 1
fast_scan.pars.disp_mot2 = 1

Now:

# yml
- class: FullFieldTomo
  rand_y_axis: $test_fulltomo_rand_spy
  rand_z_axis: $test_fulltomo_rand_spz

# python
fast_scan.pars.rand_disp_y = 1
fast_scan.pars.rand_disp_z = 1