Use `env delete` command in VSCode extension

[bwateratmsft]

Depends on #937. When the env delete command is available, we should use it in the VSCode extension instead of simply deleting the files.

[rajeshkamal5050]

@bwateratmsft this is getting addressed as part of #3285 for the March iteration. Once done, can we add this to the VSCode Azd Extension?

[bwateratmsft]

Of course!