Cleanup cake file, add targets, fix for iOS Pair

[PureWeen]

Description of Change

• Deleted all of the tasks in build.cake AFAIK none of these are currently used. At a later point if we need to re-enable the CG tasks we can add them back in using more current tools
• Added Task VS: to procure dotnet, builds maui, opens maui.slnf
  • Added --clean argument which will delete the bin/obj folders
  • Added --sln argument so you can specify a different sln file you want VS to open with the local install of dotnet.
    • If you also want to force another pack you can add a --pack.
  • The VS target will now open VS regardless of failures in the code. If you want to just see build errors in the CLI then you can run the dotnet-buildtasks target instead of the VS target
• Added some code that outputs a dotnet-sdk-version.txt file with the dotnet version. iOS Pair to mac currently needs this so it can download the correct dotnet version

Once this is merged I'll updated development.md because that's probably going to be a bit of a discussion.

EXAMPLE

Install dotnet, pack maui, and open external Solution. This is useful for validating a PR against a users Repro
dotnet cake --sln="<download_directory>\MauiApp2\MauiApp2.sln" --target=VS --pack

Install dotnet and open external Solution. This is useful for validating a PR against a users Repro. If you've already packed MAUI and don't want it to run pack again
dotnet cake --sln="<download_directory>\MauiApp2\MauiApp2.sln" --target=VS

Install dotnet, delete all bin/obj, open external Solution.
dotnet cake --sln="<download_directory>\MauiApp2\MauiApp2.sln" --target=VS --clean

[rmarinho]

Love this, my only request is can we have a option that installs workloads, builds the sln and even if there0s erros it still opens VS with sln. sometimes getting to test new maestro bump the api breaks, and when I build it doesn't open vs with the local workloads because the sln failed to build, but I wanted to fix the API on VS, not manually. SO maybe a --force option?

[PureWeen]

@rmarinho good point. I feel like just opening VS should always be the default :-) That's the point of the cake script anyway right? If you don't want to open VS then just run cli commands

[mattleibow]

Looks good. Probably need verify that the nugets have all the same content after CI is done just to be really sure.