Add _to_manifest_key method for asset path resolution

[mhxion]

Fixes #1. The issue does not happen with run_detectors because run_detectors use ensure_assets_for_config method that does the correct comparison between the two paths. So if we just use the same solution it just works. I have added the _to_manifest_key where this path resolution happens so it's nice and clean.

I would have also liked to throw an error and abort in line 108:

nicetoolbox/nicetoolbox/download_manager/manager.py

Lines 106 to 109 in 7026214

	for key in set(asset_keys):
	if key not in self.manifest:
	logging.warning(f"Asset key '{key}' not found in asset_manifest.toml.")
	continue

So when the download fails due to path error, the download_assets does not exit with code 0! But that is workflow dependent, and maybe for you this is the desired behavior. So I will leave that as is.