ENH: move winHandle.activate() to beginning of run()

[mh105]

Following #6874, we need to call win.winHandle.activate() at the beginning of run() instead of immediately before the first win.flip(). This is because certain custom code could also trigger the lost focus if the code gets inserted to Beginning of Experiment. This way the window is ensured to be on the foreground at the very beginning of an experiment.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.63%. Comparing base (c1992f5) to head (9911f90).
Report is 3 commits behind head on release.

Additional details and impacted files

@@           Coverage Diff            @@
##           release    #6876   +/-   ##
========================================
  Coverage    49.62%   49.63%           
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  Files          332      332           
  Lines        61208    61208           
========================================
+ Hits         30377    30380    +3     
+ Misses       30831    30828    -3     

Components	Coverage Δ
app	∅ <ø> (∅)
boilerplate	∅ <ø> (∅)
library	∅ <ø> (∅)
vm-safe library	∅ <ø> (∅)