Refactor ArrayMetadata{V3,V2} constructors

[LDeakin]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 59.00000% with 41 lines in your changes missing coverage. Please review.

Project coverage is 81.83%. Comparing base (a81bc89) to head (5dd270a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
zarrs_metadata/src/v2/array.rs	0.00%	41 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #97      +/-   ##
==========================================
- Coverage   81.95%   81.83%   -0.13%     
==========================================
  Files         166      166              
  Lines       23415    23481      +66     
==========================================
+ Hits        19190    19215      +25     
- Misses       4225     4266      +41     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.