Terminal suggest: Support resolving environment variables in directories

[Tyriar]

This is somewhat shell-dependent:

• We want cd $HOME to show the actual home directory on the right side. Currently our pwsh support doesn't do this:

  

  But it does resolve the actual path and show it for . and ..:

  

• We want cd $HOME/ to provide the same completions as cd ~/ for the resolved $HOME folder

• This is not just for $HOME but for any environment variable

• Different shells may have different syntax for this, but the above is the baseline which works in the majority of shells (including pwsh). Interestingly cd ${env:HOME} works when run in pwsh but cd ${env:HOME}\source and cd "${env:HOME}\source" do not