Fix CI issue with gcov

[darbyjohnston]

Summarize your change.

It looks like the gcc version in the CI may have changed which is causing issues with gcov/geninfo:

geninfo: ERROR: "/home/runner/work/OpenTimelineIO/OpenTimelineIO/src/deps/rapidjson/include/rapidjson/reader.h":271: mismatched exception tag for id 1, 1: '0' -> '1'

This PR fixes the issue by removing rapidjson from the coverage. It also includes other build fixes from this PR:
#1820

[darbyjohnston]

@reinecke It looks like this change fixes the gcov error, but now there is also a different error for the Windows/msys build:

Run curl -sS https://bootstrap.pypa.io/get-pip.py | python
error: externally-managed-environment

This environment is externally managed

To install Python packages system-wide, try 'pacman -S
$MINGW_PACKAGE_PREFIX-python-xyz', where xyz is the package you
are trying to install.

If you wish to install a non-MSYS2-packaged Python package,
create a virtual environment using 'python -m venv path/to/venv'.
Then use path/to/venv/bin/python and path/to/venv/bin/pip.

If you wish to install a non-MSYS2 packaged Python application,
it may be easiest to use 'pipx install xyz', which will manage a
virtual environment for you. Make sure you have $MINGW_PACKAGE_PREFIX-python-pipx
installed via pacman.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.
Error: Process completed with exit code 1.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.75%. Comparing base (c0e97b0) to head (f9f2739).
Report is 31 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1823      +/-   ##
==========================================
+ Coverage   84.11%   84.75%   +0.63%     
==========================================
  Files         198      176      -22     
  Lines       22241    12711    -9530     
  Branches     4687     1181    -3506     
==========================================
- Hits        18709    10773    -7936     
+ Misses       2610     1760     -850     
+ Partials      922      178     -744     

Flag	Coverage Δ
py-unittests	84.75% <ø> (+0.63%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
tests/test_clip.py	98.00% <ø> (+0.19%)	⬆️

... and 128 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 68d891a...f9f2739. Read the comment docs.