CALM Schema 1.2 - decorators

[jpgough-ms]

Initial draft of #1864

[markscott-ms]

Required
Please retarget this onto the release-1.2-revised branch, and to the calm/release/1.2/meta folder.

Optional
@jpgough-ms are you able to make #2090 ?

Leigh, Ross and I intend to discuss the Timelines schema change #2091 / #2100 , and how much of associated tooling we want to release at the same time rather than afterwards (AI is 'done', basic validation is done; documentation, visualisation, vscode support, and advanced validation are not done).

The same considerations would apply to decorators - is it just a schema update, or lots of associated tooling etc. The desire is to keep the release branch short lived as possible to avoid significant deviation from main and the merge conflicts that result.

[jpgough-ms]

@markscott-ms moving this to a new PR and will provide some examples.