fix to avoid replacing charts with the Loading logo when charts are n…

[jpchev]

this is to fix issue 27532

SUMMARY

by setting to True the following feature flag in config.py

"DASHBOARD_DISABLE_LOADING": True

one can avoid having charts replaced by the login icon when charts are not in the current view.
This is useful to export all the charts of a dashboard to a pdf file.

TESTING INSTRUCTIONS

after having set the feature flag DASHBOARD_DISABLE_LOADING, see in the DOM that charts don't get replaced by the "loading" img upon scrolling the page.

Fixes #27532

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.85%. Comparing base (76d897e) to head (01e6dce).
Report is 974 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #30935       +/-   ##
===========================================
+ Coverage   60.48%   83.85%   +23.36%     
===========================================
  Files        1931      536     -1395     
  Lines       76236    38959    -37277     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    32670    -13444     
+ Misses      28017     6289    -21728     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	48.82% <ø> (-0.35%)	⬇️
javascript	?
mysql	76.69% <ø> (?)
postgres	76.81% <ø> (?)
presto	53.30% <ø> (-0.51%)	⬇️
python	83.85% <ø> (+20.36%)	⬆️
sqlite	76.28% <ø> (?)
unit	60.82% <ø> (+3.20%)	⬆️

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