[FR] Add option for plugins to add header actions

[matmair]

Fixes #8593
Follow up to #9283

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[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 86.57%. Comparing base (499e48c) to head (ea97ab2).

Files with missing lines	Patch %	Lines
src/backend/InvenTree/plugin/base/ui/tests.py	50.00%	3 Missing ⚠️
...lugin/samples/integration/user_interface_sample.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9570   +/-   ##
=======================================
  Coverage   86.57%   86.57%           
=======================================
  Files        1243     1243           
  Lines       54665    54674    +9     
  Branches     2230     2229    -1     
=======================================
+ Hits        47327    47335    +8     
- Misses       6772     6773    +1     
  Partials      566      566           

Flag	Coverage Δ
backend	88.52% <60.00%> (+<0.01%)	⬆️

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