[packchk]: Warning if `<trace>` element contains `Pname` attribute

[jreineckearm]

Describe The Problem To Be Solved

Open-CMSIS-Pack/Open-CMSIS-Pack-Spec#415 deprecates (or actually removes) the Pname attribute from the <trace> element. We should issue a warning to pack implementers that this should no longer be used.

Note: I checked this isn't used in public PDSC found in a freshly updated .Web folder.

(Optional): Suggest A Solution
As written above.