Add normalisation logic to VCS URL

[Alex-Stevens]

An attempt to normalise the contents of the VCS URL to handle SCP-like Git URLs.

The behaviour is to:

• Skip adding the external reference in the event the VCS URL cannot be normalised.
• Add the https URL scheme (because modifying it to this scheme worked when cloning from GitHub, unlike alternatives).

I successfully validated the produced SBOM and uploaded it to Dependency Track.

#890