Add Open Schema button to Topic Hierarchy view

[knolleary]

Part of #4919

Adds a button to the header of the Topic Hierarchy view to open the generated AsyncAPI in a new window.

Also noticed the generated schema ought to have a security section - so added.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.37%. Comparing base (ff70a8a) to head (f8f3f90).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5008   +/-   ##
=======================================
  Coverage   78.37%   78.37%           
=======================================
  Files         328      328           
  Lines       15438    15438           
  Branches     3559     3559           
=======================================
  Hits        12099    12099           
  Misses       3339     3339           

Flag	Coverage Δ
backend	78.37% <ø> (ø)

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[cstns]

confirmed working locally