Restructure crates into _model structure.

[azriel91]

• Addresses part of Move types to *_model and *_rt_model crate structure  #187.

Still need to move the peace_cmd (the CmdCtx builder types), and then the *Cmd types out of peace_rt.

[codecov]

Codecov Report

Attention: Patch coverage is 81.41593% with 21 lines in your changes missing coverage. Please review.

Project coverage is 88.43%. Comparing base (17278be) to head (f4aca08).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
crate/rt_model/src/item_wrapper.rs	0.00%	7 Missing ⚠️
crate/rt_model/src/params_specs_serializer.rs	0.00%	6 Missing ⚠️
...e/webi_output/src/outcome_info_graph_calculator.rs	0.00%	2 Missing ⚠️
items/blank/src/blank_item.rs	0.00%	1 Missing ⚠️
items/file_download/src/file_download_item.rs	0.00%	1 Missing ⚠️
items/sh_cmd/src/sh_cmd_item.rs	0.00%	1 Missing ⚠️
items/tar_x/src/tar_x_item.rs	0.00%	1 Missing ⚠️
workspace_tests/src/mock_item.rs	0.00%	1 Missing ⚠️
workspace_tests/src/vec_copy_item.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #202      +/-   ##
==========================================
+ Coverage   88.38%   88.43%   +0.04%     
==========================================
  Files         432      430       -2     
  Lines       45220    45137      -83     
==========================================
- Hits        39969    39916      -53     
+ Misses       5251     5221      -30     

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