Cleans up the blank starter template

[dotMorten]

Description of Change

Issue: #26484

Removes resources and XAML that are always going to be deleted. The "Include Sample Content" will instead be the way to get starting content beyond a blank project.
The problem with the current "blank" template is that it adds a lot of content that you always have to delete, adding extra steps. It also removes the dotnet_bot.png that most of us always forget to delete, since no app will actually include it in the end.
This ensures that users are set up to start working without first having to clean up sample content.

If the user does want sample content / a tutorial, they can check the new "Include Sample Content" checkbox that was introduced in 9.0 and still get sample code as a starting point.

As a side benefit, the sample-content version was never actually referencing the dotnet_bot.png file, so it was just wasteful content that is now also cleaned up with this PR.

It also creates consistency with existing WPF template, as well as the work that is currently happening in the WinUI project template.

Tested by manually building the templates projects and installing it from commandline. Tested both via CLI and VS

Fixes #26484

[dotnet-policy-service]

Hey there @dotMorten! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[dotMorten]

@jfversluis As discussed ;-)

[PureWeen]

Any version of this would have to wait until .NET 10

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Redth]

I don't believe there's enough signal to make such a change yet.

What I could see doing is adding this as another parameter option to the template (eg: --empty) and pivoting the template to remove some things or change some things depending on if this is set or not.

If we did this, one of the items we need to still look at is if we can make pivoting on those template parameters more simple. It seems like other templates basically pivot the entire template based on a parameter which keeps things neatly separated, vs right now we have a bunch of #ifdef type logic in one giant template.

In either case we'd also need to make sure the behaviour works correctly if you try to use --sample-content and --empty together? ie: is there a way to declare parameters that are mutually exclusive?

In any case, this is not a change we're prepared to make in this current form, though the discussion is appreciated. Is there an existing issue or discussion in our repo we can link this to? I'd prefer to see these discussions happen before you spend your time on creating a PR that we might not merge :)

[dotMorten]

@Redth Issue: #26484

[jfversluis]

Converting to draft for the time being while we discuss a bit first, see linked issue!