Enable automatic install of templates on first use

Was thinking, it would enable a lot of ease and usage if the templates can be used without installing it using dotnet new. Can we just use those templates directly from the nugets or a folder to create those items derived from the templates. It may be available now, not sure, but I could not see any available solution for the same.

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**Audience**: dotnet CLI users

### Background
Now to instantiate any template you need to install the package containing it first.
The packages are not updated automatically, and it's user responsibility to keep the up-to-date. To check updates the user needs to use `update` command or will be prompted only after outdated template is created.
In many cases, when acquiring new template, it would be beneficial to try it first to see if it matches your needs.
Now it is a 3 step process:
- install the template package
- instantiate the template
- uninstall the template package

### Justification
- even better experience for CLI users
- easy option to "try it out" before installing the package
- avoid running outdated templates - always use latest from the source
- popular tools like npx has this experience