Support snapping to elements inside orthogonal view attachments

[pmconne]

Fixes #5585.

Viewport.readPixels will now include the Id of the view attachment, if any, from which the hit originated.
HitDetail can have a ViewAttachmentHitInfo which includes that view attachment Id along with (marked as @alpha - for internal consumption only!) the Viewport used to render the attachment into the sheet view.
ViewState.computeDisplayTransform now accepts an optional view attachment Id, which a sheet will use to provide the transform from that attachment's model space to the sheet's model space.
AccuSnap will populate the SnapRequestProps using the view attachment's viewport if present, instead of the screen viewport.
The inverted display transform is applied to hit points when making the request, and the display transform is applied to sprite and hit decoration locations.

I had to add yet another optional argument to HitDetail, which already took over a dozen arguments. I overloaded that constructor to take a single object and deprecated the old one.

[pmconne]

@ben-polinsky @MichaelBelousov transformer docs still breaking this PR. New error.

Starting: Download Transformer Docs Docs Artifact
==============================================================================
Task         : Download Pipeline Artifacts
Description  : Download build and pipeline artifacts
Version      : 2.198.0
Author       : Microsoft Corporation
Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/download-pipeline-artifact
==============================================================================
Download from the specified build: #2212613
Download artifact to: D:\vsts_a\3/Transformer Docs
##[error]Artifact Transformer Docs was not found for build 2212613.
Finishing: Download Transformer Docs Docs Artifact

[ben-polinsky]

@pmconne Once this pr merges you should be good to go.