Add official copy of the Arcade templates that is compatible with 1ES…

[riarenas]

… pipeline templates schema

#14524

Adds a new set of templates that are compatible with the 1ES PT schema.

For now, these are mostly just a carbon copy of the public templates, some notable changes to show the kinds of improvements / cleanup we can make afterwards:

• The post-build.yml stage does not run SDL anymore as that's supposed to be taken care of by the official pipeline templates.
• The pool-providers template only gets you a variable for an internal pool, this will error out if trying to run in the open with the $(dncengpublicbuildpool) variable.

I used these templates to build Symreader here: https://dnceng.visualstudio.com/internal/_build/results?buildId=2390282&view=results

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/arcade/tree/main/Documentation/Validation

[riarenas]

I'll try to come up with something to get us a decent diff between this and the unofficial templates to see what the actual changes were

[riarenas]

I'll try to come up with something to get us a decent diff between this and the unofficial templates to see what the actual changes were

I've been failing at this so far, still trying to get something easier to look at but I wouldn't wait on that.

[riarenas]

@mmitche @dougbu or @chcosta I think this is good to go again. PTAL at your earliest convenience