Add pwsh provisioner to linux

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#### Description

Add support for using the powershell provisioner on linux. I'm currently using the standard shell provisioner and changing the run command like so:
```
provisioner "shell" {
execute_command = "sudo sh -c '{{ .Vars }} pwsh -f {{ .Path }}'"
scripts = ["${path.root}/scripts/Install-stuff.ps1"]
}
```
This doesn't seem to work when specifying `inline`.

#### Use Case(s)

When building linux images using pwsh as the primary scripting language instead of bash.

#### Potential configuration
I'd love it if something like this worked:
```
provisioner "pwsh" {
inline = [ "Write-Host \"Hello from PowerShell\""]
}
```