docs: Update the installation guide

[munechika-koyo]

Description

Since raysect has been updated to v0.9, we should revise the installation guide page in the document.

Some proposed changes

• Update the prerequisites:
  • For runtime: python v3.9+, numpy, and matplotlib
  • For buildtime: python v3.9+, numpy v2+, cython v3.1+, meson-python, and setuptools-scm
• Replace setup.py installation with pyproject.toml to install from the source.
  • python setup.py install -> python -m pip install .
• Update the testing guide.
  • Replace nose testing description with a simple unittest.