Update ESM4.2 yaml configurations

[singhd789]

Describe the bug
There has been a lot of yaml development and updates since these yaml configurations were added here. In order for these configs to work, they need to be updated.

In esm4.yaml:

• move directories and postprocess section to own ./pp/settings.yaml for example

• add settings.yaml path under experiment's pp:

     experiments:
         - name: "ESM4p2_piControl_spinup_J"
           pp: 
               - "settings.yaml"
  

• remove shared section

In new pp/settings.yaml:

• in [postprocess][settings]:
  - can add keys: pp_chunks, pp_start, pp_stop, pp_grid_spec if needed/defined
  - for pp_chunks (pp_chunk_a and pp_chunk_b were replaced by pp_chunks)

pp_chunks:
    - *PP_CMIP_CHUNK_A
    - *PP_CMIP_CHUNK_B

• in [postprocess][switches]:
  - remove do_statics
  - add do_analysis_only