Run Pester tests using single quotes for test name

This change causes Pester tests run with the "Run/Debug Tests"
CodeLenses to be launched using single quotes with the `-TestName`
parameter so that variable names in the test name don't get expanded.

Resolves #891

Author: daviwil

Diff for: src/features/PesterTests.ts

@@ -41,7 +41,7 @@ export class PesterTestsFeature implements IFeature {
             args: [
                 `-Script "${uri.fsPath}"`,
                 describeBlockName
-                    ? `-TestName "${describeBlockName}"`
+                    ? `-TestName '${describeBlockName}'`
                     : ""
             ],
             internalConsoleOptions: "neverOpen",