Add inventory-item-has-vendor-name constraint

[Gabeblis]

Committer Notes

Purpose

This PR aims to add the inventory-item-has-vendor-name constraint which ensures that every inventory item has a "vendor-name" FedRAMP extension prop, either on the inventory-item itself or within the component linked to the inventory-item.

Changes

Added constraint:

• inventory-item-has-vendor-name

Added valid/invalid test content:

• ssp-inventory-item-has-vendor-name-INVALID.xml
• Edited fedramp-ssp-example.oscal.xml to align with constraint

Added yaml files for testing:

• Pass/fail yaml tests added for each of the above constraints.

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[Rene2mt]

PR looks good!! Unrelated to changes made in this PR, there are some invalide component UUID references in the example SSP inventory, however, those can be fixed separately (I created #1049 to address that).