Add a JsPromise::from_result for convenience

[hansl]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 52.88%. Comparing base (6ddc2b4) to head (51fdfab).
Report is 290 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/object/builtins/jspromise.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4039      +/-   ##
==========================================
+ Coverage   47.24%   52.88%   +5.64%     
==========================================
  Files         476      483       +7     
  Lines       46892    46947      +55     
==========================================
+ Hits        22154    24829    +2675     
+ Misses      24738    22118    -2620     

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

[nekevss]

LGTM