Fix two developer-facing annoyances

[alexreinking]

Two small things have been bothering me for a while:

1. I used python instead of python3 in the custom pre-commit commands. These require an active virtual environment, which is annoying when you aren't working on anything Python-related and are using system dependencies.
2. The naming of the cmake/vcpkg folder is inconsistent with cmake/vcpkg-triplets and a little misleading in that it sounds like a submodule checkout of vcpkg. Rename that to cmake/vcpkg-ports to indicate that it contains ports.

Checklist

• Documentation updated (if public API changed)
• Commits include AI attribution where applicable (see Code of Conduct)

[alexreinking]

Running buildbots to make sure I didn't inadvertently break the vcpkg configuration.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@2834ffe). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9133   +/-   ##
=======================================
  Coverage        ?   69.77%           
=======================================
  Files           ?      255           
  Lines           ?    77531           
  Branches        ?    18538           
=======================================
  Hits            ?    54094           
  Misses          ?    17949           
  Partials        ?     5488           

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