fix(ocaml): Improve OCaml releaser for monorepos

[phated]

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Closes #864
Closes #865
Closes #866 🦕

[phated]

I have a patch for #866 but the tests are failing for some snapshot thing so I'll figure that out before including. Added here.

[codecov]

Codecov Report

Merging #867 (5e8028b) into master (da15626) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #867      +/-   ##
==========================================
+ Coverage   94.27%   94.29%   +0.02%     
==========================================
  Files          68       69       +1     
  Lines        9600     9638      +38     
  Branches      982     1040      +58     
==========================================
+ Hits         9050     9088      +38     
  Misses        547      547              
  Partials        3        3              

Impacted Files	Coverage Δ
src/releasers/ocaml.ts	100.00% <100.00%> (ø)
src/updaters/ocaml/dune-project.ts	100.00% <100.00%> (ø)

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[bcoe]

@phated thanks for fixing this up 👍