Provide prose explaining the use of guids across all occurrences

[sthagen]

During the TC meeting 2024-07-11 the discussion made explicit, that the use cases for the diverse guid elements require a clear guidance in the prose.

As example it should be made clear what consequences are expected if for two or more SARIF files targeting the same analysis target, the corresponding guid fields (root object or else):

• share the same value
• have different values