NPI-4175 Revise filename property extraction functionality

[treefern]

This PR improves robustness and error checking, in functionality for statically extracting properties from filenames.

Notably:

• The regex for extraction of IGS long format filenames has been extended to completely encompass the specification. This allows:
  • Parsing Long Term Product filenames (which have a start epoch and end epoch, rather than a start epoch and period)
  • Reading whether file is compressed (.gz) or not. Note that this is technically part of the filename specification. Previously, passing .SP3.gz would result in an error and had to be trimmed first.
  • Reading filenames containing a Station ID
• Adds multiple strictness / check options (most are off by default for compatibility). Among other things, this allows restricting to only long format filenames and raising exceptions for everything else.
• Adds general (likely too permissive) regex for approximately checking IGS short format filenames. Warnings or exceptions can be raised if this does not pass.

[ronaldmaj]

I've tested this locally with a couple files I have. Seems to work fine with those. I've also had a look through the code and don't see anything that jumps out as a big issue.
Happy for this to go in, especially as it will help with recent work.

[ronaldmaj]

The change was an update to a comment - still happy for this to go in 👍