fix: add coerce_to_multiOmicDataSet() for backward compatibility

[kelly-sovacool]

Changes

• coerce objects to current MOObject::multiOmicDataSet to preserve backward-compatibility with MOSuite from prior to v0.5.0.

Issues

None

PR Checklist

(Strikethrough any points that are not applicable. Check boxes only, do not append descriptions.)

• This comment contains a description of changes with justifications, with any relevant issues linked.
• Write unit tests for any new features, bug fixes, or other code changes.
• Update the docs if there are any API changes (roxygen2 comments, vignettes, readme, etc.).
• Update NEWS.md with a short description of any user-facing changes and reference the PR number. Follow the style described in https://style.tidyverse.org/news.html
• Run devtools::check() locally and fix all notes, warnings, and errors.

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.63%. Comparing base (377c5ff) to head (f3526cb).

Files with missing lines	Patch %	Lines
R/multiOmicDataSet.R	89.47%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              main      #13      +/-   ##
===========================================
- Coverage   100.00%   98.63%   -1.37%     
===========================================
  Files            1        1              
  Lines          258      293      +35     
===========================================
+ Hits           258      289      +31     
- Misses           0        4       +4     

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