[frontend] Changes to helper text for search widgets

[ParamConstructor]

Proposed changes

This PR updates the helper text in the search widgets of OpenCTI to more clearly convey what the search target of the widget is:

• Top Right widget now says 'Search OpenCTI...' since this widget searches the whole platform
• Top Left widget nested within a section now says 'Search these results....'
• The SearchInput component was updated to accept a 'placeholder' value which is defaulted to the 'Search these results' option but can be overload - like in TopBar to be replaced with 'Search OpenCTI'

Related issues

• None

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d040085) 87.27% compared to head (626afb1) 87.27%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4915   +/-   ##
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  Coverage   87.27%   87.27%           
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  Files           3        3           
  Lines         220      220           
  Branches       55       55           
=======================================
  Hits          192      192           
  Misses         28       28           

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