Add 'terminalQuoteCharacter' to the debug configuration we send to debugpy

[rchiodo]

In order to fix microsoft/debugpy#1980, the debugger needs to quote the values it sends in the 'runInTerminal' request. However the quote being used depends upon the terminal that will eventually be used.

For example, quote a string this way:

"C:\My Dir With Spaces\python.exe"

will fail on powershell, but succeed on cmd.exe

Powershell requires single quotes like so:

'C:\My Dir With Spaces\python.exe'

This PR adds a new terminalQuoteCharacter to the debug configuration we send to debugpy. A follow up PR in debugpy will use this value to properly quote arguments in the 'runInTerminal' reverse request.