Improvement: add context hooks in CMakeLists.txt

[dutkalex]

Describe your changes here:
This PR enables clearer configure logs when invoking CMake with -DCMAKE_MESSAGE_CONTEXT_SHOW=ON: the logs feature a context prefix [p4est] or [sc] when configuring p4est and sc. This is purely opt-in, and composes nicely with downstream projects, which can use the same pattern to obtain [t8code.sc] for example.

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General

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.41%. Comparing base (4749d46) to head (d0c44b6).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1838   +/-   ##
=======================================
  Coverage   74.41%   74.41%           
=======================================
  Files         101      101           
  Lines       19190    19190           
=======================================
  Hits        14280    14280           
  Misses       4910     4910           

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