Improve Azure Pipelines template hygiene

[lbussell]

There is a wide variety of quality in the Azure pipelines templates hosted in this repo. We should go through all of the templates and:

• Convert any implicitly typed template parameters to type-safe parameters.
• Ensure parameter defaults are only set in one place (for parameters that are passed through multiple template levels).
• Document any parameters or variables which aren't commented/documented somewhere at least once.
• Put quotes around strings wherever possible
  • This is to prevent unexpected conversions to numbers, dates, etc. These are well documented issues with yaml.

[lbussell]

We could enforce this with yamllint but it would add a test/CI dependency on python which I don't love.

Super-linter (which we already use in dotnet-docker) supports yamllint.