fix: Pack add-ins discovery targets with the dev-server (backport #19464)

[mergify]

linked to unoplatform/studio#43 (comment)

Bugfix

Pack add-ins discovery targets with the dev-server to be able to run them no matter the SDK sued by the project

What is the current behavior?

If a project uses the Microsoft.NET.Sdk the add-ins discovery might fail.

What is the new behavior?

Targets are dynamically injected, no matter the SDK

PR Checklist

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• Commits must be following the Conventional Commits specification.

---

This is an automatic backport of pull request #19464 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 36a0d9b has failed:

On branch mergify/bp/release/stable/5.6/pr-19464
Your branch is up to date with 'origin/release/stable/5.6'.

You are currently cherry-picking commit 36a0d9b107.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   src/Uno.UI.RemoteControl.Host/DevServer.Custom.Targets
	modified:   src/Uno.UI.RemoteControl.Host/Extensibility/AddIns.cs
	modified:   src/Uno.UI.RemoteControl.Server.Processors/Helpers/ProcessHelper.cs
	modified:   src/Uno.UI.RemoteControl/buildTransitive/Uno.WinUI.DevServer.targets

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Uno.Sdk/targets/Uno.Build.targets

Cherry-pick of f980d05 has failed:

On branch mergify/bp/release/stable/5.6/pr-19464
Your branch is ahead of 'origin/release/stable/5.6' by 1 commit.
  (use "git push" to publish your local commits)

You are currently cherry-picking commit f980d05414.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/Uno.UI.RemoteControl.Host/DevServer.Custom.Targets
	modified:   src/Uno.UI.RemoteControl.Host/Extensibility/AddIns.cs
	modified:   src/Uno.UI.RemoteControl.Host/Uno.UI.RemoteControl.Host.csproj
	modified:   src/Uno.UI.RemoteControl/buildTransitive/Uno.WinUI.DevServer.targets

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/Uno.Sdk/targets/Uno.Build.targets

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally