Integrate template localizer into arcade

[bekir-ozturk]

To allow all repos under dotnet to easily localize templates, we are looking to integrate TemplateLocalizer task into arcade.
I'm not a 100% sure if this is the right way to implement this, so here is an early draft PR.

The intent is to allow turning template localizations on a repo, simply by setting "UsingToolTemplateLocalizer" property to true.
This is very much like how Xliff tools are setup (except for throwing errors on CI), so my changes here are very similar to what was done for Xliff tools.

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/core-eng/tree/master/Documentation/Validation (Changes are not unit-testable. But generated arcade.sdk package was tested locally. No issues.)

[bekir-ozturk]

@jonfortescue Can you check to see if this looks OK?

[vlada-shubina]

fully support the change, having it available via arcade will simplify many template repos onboarding.

[vlada-shubina]

will this be updated automatically?

[bekir-ozturk]

Initially, no. But we should have some update method eventually, whether it is automatic or manual. For the time being, my current focus is to get this running smoothly on all dotnet repos which includes templates.

[riarenas]

I see that this package has entries in the BAR, so it should be simple to set up a maestro subscription so that this version gets updated automatically. We can set that up once this is merged and you're happy with how it's working.

[bekir-ozturk]

Thanks @riarenas, that sounds great! I will ping you if that's OK, once I confirm that everything is running fine.

[jonfortescue]

This looks great to me, as long as you've made sure it's tested and working!

cc/ @markwilkie for visibility

[markwilkie]

nice!