Add SiteExtension.proj to replace build-extension.ps1

[jviau]

Issue describing the changes in this PR

resolves #issue_for_this_pr

Pull request checklist

IMPORTANT: Currently, changes must be backported to the in-proc branch to be included in Core Tools and non-Flex deployments.

• Backporting to the in-proc branch is not required
  • Otherwise: Link to backporting PR -- TODO
• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• My changes do not require diagnostic events changes
  • Otherwise: I have added/updated all related diagnostic events and their documentation (Documentation issue linked to PR)
• I have added all required tests (Unit tests, E2E tests)

Additional information

This PR introduces a new project WebHost.Script.SiteExtension, which is a replacement for build-extension.ps1. This project can be used via dotnet CLI to restore, build, and publish all the artifacts needed for the Antares site extension. Note that this project has support for multi-targeting, but only targets a single TFM. This is in preparation for porting to in-proc branch to keep the diff minimal between the two.

Other Changes

• Removes update-hostreferences.ps1, this is no longer used anywhere
• Groups all worker versions into workers.props file. Left python out due to code owners, but ideally python will be moved there as well.
• zip-after-publish is extracted into a set of re-usable targets ZipPublish.targets.
• RuntimeIdentifiers added to WebHost.csproj. Having this set of identifiers listed improves the restore task (otherwise each time you want to use a different runtime, you have to re-restore).

[kamperiadis]

@jviau Just as a heads up, we have recently updated the java worker version so that appears to be causing conflicts for your PR.

[liliankasem]

@jviau is this PR still relevant?

[jviau]

@liliankasem yes, I plan on merging it in soon. Was just waiting for the current release to be cut. But that has been done so I will update this PR soon :)