"Treat backslash as escape characters for SQL" fails for SQLCMD mode :setvar script

[JamieOglethorpeEPS]

Description of the Issue

A :setvar command uses double quotes for the value part:
:setvar DefaultDataPath "C:\EPS\Data\"

The backslash is treated as an escape character regardless of the setting.
This example was generated by SqlPackage.exe

Steps to Reproduce the Issue

1. Create a new document (e.g. ctrl-n)
2. Set the language to SQL
3. Capture the following two lines:
   "\"
   GO

Expected Behavior

The GO command should be blue

Actual Behavior

The GO command is grey.

Debug Information

Screenshot:

Reference: Issue 2451

[dail8859]

Turn off Settings > Preferences > MISC > Treat backslash as escape character for SQL

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