Simplify build yml

[scbedd]

Setting some context

This change is best explained in pictures. A standard build looks like this:

With the job dependencies as shown

Build
  -> Build_Extended
    -> Analyze
  -> TestN

When an extension package is present, this changes. (indicated by AdvancedBuild boolean from ci.yml)

Build_Linux
Build_Windows
Build_Mac
  -> Coalesce Artifacts
    -> Build_Extended
      -> Analyze
    -> TestN

As you can see. The build is bigger when we know we have an extension package present. But what about when we don't know at template compile time if we have an extension package? That's the world we're heading for with the pipelinev3 efforts.

This PR is setting the stage to allow a PR build which expands and contracts to handle when azure-storage-extensions is detected to be part of the necessary build set.

What this PR does

• Removes compile-time difference between advanced and non-advanced builds
• Allows run-time detection of storage service directory to produce non-linux artifacts when azure-storage-extension is detected
• Uses ENABLE_EXTENSION_BUILD to skip the build tasks on windows and mac when azure-storage-extension (or any extension package later) is NOT detected

And the job dependencies will look like:

Build_Linux
Build_Windows (steps skipped if no extension package)
Build_Mac (steps skipped if no extension package)
  -> Build_Extended
    -> Analyze
  -> TestN