Use virtual environments in CI workflows

[zachcran]

Description

Some CI workflows are not isolating the packages used during testing in a virtual environment. This could lead to picking up already installed packages that may have come with the default installation (for example, the ubuntu-24.04 image comes preinstalled with Python 3.12.3 (link).

List of workflows that...

Need virtual environments added

• .github/workflows/test_pip_install.yaml
• .github/workflows/tag_and_release.yaml (technically actually the reusable workflow at CMakePP/.github/.github/workflows/pypi_release_master.yaml; issue TBD)

Use an unconventional venv name (not venv or .venv)

• .github/workflows/deploy_docs.yaml
• .github/workflows/pip_install.yaml