[AOT] Resolve Trimming warnings in ActivityInstrumentationHelper

[eerhardt]

The trimming tool can't tell which type Expression.Property(Expression, string propertyName) refers to, so it isn't able to preserve the referenced property.

The workaround is to explicitly reference the PropertyInfo from the static type, which the trimmer can see and knows to preserve the property.

Contributes to #3429

Merge requirement checklist

• CONTRIBUTING guidelines followed (nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Merging #4513 (2afaee3) into main (30ad91a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4513      +/-   ##
==========================================
+ Coverage   85.13%   85.17%   +0.03%     
==========================================
  Files         316      316              
  Lines       12581    12583       +2     
==========================================
+ Hits        10711    10717       +6     
+ Misses       1870     1866       -4     

Impacted Files	Coverage Δ
...elemetry/Internal/ActivityInstrumentationHelper.cs	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes