irmin-pack-utils: Add printer to json for control file

[clecat]

This PR is meant to give a tool for an easy reading of the control file. It contains:

• The addition of an irmin-pack-utils package for irmin-pack related tools.
• A tool named irmin-ppcf which prints the content of a given control file in a json format (which can then be pretty printed with tools like jq).
• The public exposure of functions required by irmin-ppcf: Because it is meant to be a debugging tool, we want to avoid most of the unnecessary computations/computations which would fail on a corrupted control file; for now, the checksum verification and the auto-upgrade to the latest version of the control file.

[clecat]

The names I have chosen for my modifications, raw_payload and of_bin_string_unsafe, might not be the most appropriate and I simply didn't come with something better, please feel free to give any suggestions about them

[clecat]

Now way cleaner, I removed the code duplication and used instead the version with the checksum, the only thing avoided is the upgrade to the latest version (since we do not want it). I also merged irmin-tezos-utils & irmin-pack-tools. While waiting for the classification of the Volume, the tool will ask for an argument (either Upper or Volume).

[codecov-commenter]

Codecov Report

Merging #2197 (2c91dcc) into main (84dcea5) will decrease coverage by 0.03%. The diff coverage is 18.18%.

:exclamation: Current head 2c91dcc differs from pull request most recent head da17778. Consider uploading reports for the commit da17778 to get more accurate results

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@@            Coverage Diff             @@
##             main    #2197      +/-   ##
==========================================
- Coverage   68.14%   68.11%   -0.03%     
==========================================
  Files         135      135              
  Lines       16294    16305      +11     
==========================================
+ Hits        11103    11106       +3     
- Misses       5191     5199       +8     

Impacted Files	Coverage Δ
src/irmin-pack/unix/control_file.ml	87.80% <0.00%> (-3.73%)	:arrow_down:
src/irmin-pack/unix/control_file_intf.ml	82.14% <33.33%> (-13.32%)	:arrow_down:
src/irmin-fs/unix/irmin_fs_unix.ml	68.38% <0.00%> (+0.64%)	:arrow_up:

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