feat: .NET7 in Lunar

[cjdcordeiro]

needs canonical/chisel#50

Changes

• add new slice definitions files for .NET7
• modify globs in .NET6 slice definitions files, to avoid path conflicts in Chisel

Definition of Ready

• atm, dotnet-host-7.0 is avoiding Chiselling conflicts by copying the dotnet binary instead of inheriting its full name and path. If we merge it now and later fix the dotnet path, we will create a regression for those already chiselling .net7. Once allow multiple slices with the same content paths to co-exist within the same Chisel release chisel#50 is done, this PR can be updated and then merged

[cjdcordeiro]

closing since the release is not closed