Refactor scripts arguments handling (#456)

- remove the use of environment variables to get directory paths,
- make use of arguments / argparse instead of environment variables in `update.py` and `report.py`,
- automatically guess the data directory in `latest.py` based on the script's location,
- propagate log level to auto scripts,
- move `list_configs_from_argv` from `endoflife` module to `releasedata` module,
- use `list_products` in `latest.py` to load the product's frontmatters.

src/virtualbox.py

@@ -1,13 +1,13 @@
 import logging
 import re
 
-from common import dates, endoflife, http, releasedata
+from common import dates, http, releasedata
 
 """Fetches releases from VirtualBox download page."""
 
 EOL_REGEX = re.compile(r"^\(no longer supported, support ended (?P<value>\d{4}/\d{2})\)$")
 
-for config in endoflife.list_configs_from_argv():
+for config in releasedata.list_configs_from_argv():
     with releasedata.ProductData(config.product) as product_data:
         html = http.fetch_html(config.url)