Timed out waiting for the PowerShell extension to start when Start debugging before extension starts

### System Details

- Operating System
   Windows 10
- VS Code version
   1.40.2
- PowerShell extension version
  2019.11.0
- Output from `$PSVersionTable`
  7.0.0-preview.6
  5.1.18362.145
### Issue Description
I am experiencing a problem with running a PowerShell debug configuration.
"PowerShell: Launch a Script"
If I do not open a ps1 file first the debugger will time out waiting for PowerShell to start.
Error: Timed out waiting for the PowerShell extension to start.

#### Repro Instructions
Open VSCode
Open a **Folder** with a launch.json and a PowerShell Script
Note: **DO NOT open any POWERSHELL scripts**
Open the debugger Control + Shift + D
Launch a configuration PowerShell Launch a script.

#### Expected Behaviour
The Launch should Run

#### Actual Behaviour
Error: Timed out waiting for the PowerShell extension to start.

#### Work around
Open a PowerShell script in the editor
Extension starts PowerShell
Run the debug configuration.
It will now work.
