Make tsconfig.json selection during webpack deterministic.

Without this `configFile` option, ts-loader apparently does not
guarantee a deterministic choice of which of the three `tsconfig.json`
files below `extensions/ql-vscode` actually gets used during webpack.
This leads to very strange behavior as even removing dead code can
change which `tsconfig.json` 'wins the race'. I observed that removing
a dependence on `semmle-bqrs` from `src/view` *tended* to make
`ts-loader` choose `src/compare/view/tsconfig.json` instead.

extensions/ql-vscode/gulpfile.js/webpack.config.ts

@@ -20,6 +20,9 @@ export const config: webpack.Configuration = {
       {
         test: /\.(ts|tsx)$/,
         loader: 'ts-loader',
+        options: {
+          configFile: 'view/tsconfig.json',
+        }
       },
       {
         test: /\.less$/,

extensions/ql-vscode/src/compare/view/tsconfig.json

@@ -1,24 +0,0 @@
-{
-  "compilerOptions": {
-    "module": "esnext",
-    "moduleResolution": "node",
-    "target": "es6",
-    "outDir": "out",
-    "lib": [
-      "es6",
-      "dom"
-    ],
-    "jsx": "react",
-    "sourceMap": true,
-    "rootDir": "../..",
-    "strict": true,
-    "noUnusedLocals": true,
-    "noImplicitReturns": true,
-    "noFallthroughCasesInSwitch": true,
-    "experimentalDecorators": true,
-    "typeRoots" : ["./typings"]
-  },
-  "exclude": [
-    "node_modules"
-  ]
-}