feat: Make project root and project name overridable for monorepo

[ROCKTAKEY]

Hi, thanks for your maintenance.

I added python-pytest-project-root-override, which override project root directory to run pytest, and python-pytest-project-name-override, which override project name.

This is intended to be used to monorepo which has multiple directories to run pytest.

Background

projectile has projectile-compilation-dir for compilation directory, but project does not. project-compilation-dir was mentioned in docstring of python-pytest--project-root like below, but it actually does not exist in the project.

https://github.com/wbolster/emacs-python-pytest/blob/25d9801562a789ea5debceb1992bd528ebb4f689/python-pytest.el#L786

Though project has project-current-directory-override to override project root directory, it affects all of packages using project-root.