file helper function that ckecks if a path (with filename) exists in a list of given folders

[Mzack9999]

This is a follow up ticket of projectdiscovery/nuclei#3927 (comment)

As described in the comment it's necessary to implement a function that given a file path (relative or absolute) and an optional list of allowed paths/filenames, verify the following:

• Extract the absolute folder from allowed files and add them to the list of allowed paths
• Simplify the list of allowed paths by pruning subdirectories of upper level folders
• Check if the given file exists in any of the final list of allowed paths
• TBD?