GitHub: simplify amep version locations

[kay-ro]

Currently, the version of AMEP is stored in multiple locations on the repo. They include

• pyproject.toml
• amep/__version__.py
• doc/switcher.json
• doc/source/conf.py

this should be simplified for easy deployment.

[kay-ro]

For pyproject.toml:

[project]
dynamic = ["version"]

[tool.setuptools.dynamic]
version = { attr = "my_package.__version__" }

[kay-ro]

For doc/source/conf.py:

import sys
from pathlib import Path

ROOT = Path(__file__).resolve().parents[3]
sys.path.insert(0, str(ROOT))

from amep._version import __version__

release = __version__

[kay-ro]

plan: only location will be inside amep._version.py as __version__