`dotnetup` should support non-native architecture installs

### Prerequisites

- [x] I have read the [dotnetup documentation](https://github.com/dotnet/sdk/tree/release/dnup/documentation/general/dotnetup).
- [x] I have searched for [existing dotnetup issues](https://github.com/dotnet/sdk/issues?q=is%3Aissue%20state%3Aopen%20label%3Adotnetup).
- [x] I have searched for [existing dotnetup discussions](https://github.com/dotnet/sdk/discussions/categories/dotnetup).

### Issue type

Feature request

### Description

We should add the `--architecture` flag or `--arch` shorthand to `dotnetup sdk install` and `runtime install` (the runtime install flag will need to apply to each runtime component in the list of components to install individually) so we can support non native scenarios.

https://github.com/dotnet/sdk/pull/55082 A recent failure in CI for rosetta in the install script indicates to me that this is a higher priority item for us now.

We do need to consider whether `--arch` is correct as this may cause confusion with the `--arch` flag(s) in the .NET SDK CLI itself when it comes to `dotnet build` etc.

### dotnetup version

_No response_

Start with the dotnetup documentation and the entry points for `dotnetup sdk install` and `runtime install`; trace how each requested component selects an architecture. Done means both commands accept a chosen non-native architecture, runtime applies it to every listed component, and the option naming is resolved without CLI confusion.

Written by the indexing model from the issue text.