dotnet exec doesn't parse command line environment directives

[tmat]

Describe the bug

dotnet exec doesn't parse command line environment directives

To Reproduce

>dotnet new console
>dotnet build

>dotnet exec bin\Debug\net8.0\repro.dll
Hello, World!

>dotnet [env:X=1] exec bin\Debug\net8.0\repro.dll
Unrecognized command or argument 'bin\Debug\net8.0\repro.dll'.

Further technical details

>dotnet --info
.NET SDK:
 Version:           8.0.200
 Commit:            438cab6a9d
 Workload version:  8.0.200-manifests.a7f084b6

[baronfel]

I believe this is because exec comes from the native dotnet host, not the CLI/SDK. As a result, the features that S.CL gives to us like environment directive support simply will not apply at that layer.

[nagilson]

cc @dotnet/appmodel for consideration of this change, but we don't think it will be prioritized due to the required effort investment