Add VariableFrameDuration support

[Kyle-Ye]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 16.92%. Comparing base (68f16bb) to head (d8c18a2).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
Sources/OpenSwiftUICore/View/Graph/ViewGraph.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #390      +/-   ##
==========================================
- Coverage   19.34%   16.92%   -2.43%     
==========================================
  Files         432      411      -21     
  Lines       23329    22122    -1207     
==========================================
- Hits         4514     3745     -769     
+ Misses      18815    18377     -438     

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