Uplevel node-pty to 0.6.0-beta2

This is the first build to feature the upgrade to winpty@0.4.1 in addition to
the conversion to TypeScript and general code clean up. The most notable
change is that Git Bash no longer goes out of sync and likely a bunch of other
issues in #14613. Certain applications within WSL do not function correctly
with this build.

I tested this on Windows and Linux.

Part of #13625

npm-shrinkwrap.json

@@ -333,9 +333,9 @@
       "resolved": "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-1.0.7.tgz"
     },
     "node-pty": {
-      "version": "0.4.1",
-      "from": "node-pty@0.4.1",
-      "resolved": "https://registry.npmjs.org/node-pty/-/node-pty-0.4.1.tgz",
+      "version": "0.6.0-beta2",
+      "from": "node-pty@0.6.0-beta2",
+      "resolved": "https://registry.npmjs.org/node-pty/-/node-pty-0.6.0-beta2.tgz",
       "dependencies": {
         "extend": {
           "version": "1.2.1",

package.json

@@ -30,7 +30,7 @@
     "iconv-lite": "0.4.15",
     "minimist": "1.2.0",
     "native-keymap": "0.3.0",
-    "node-pty": "0.4.1",
+    "node-pty": "0.6.0-beta2",
     "semver": "4.3.6",
     "vscode-debugprotocol": "1.15.0",
     "vscode-textmate": "3.1.0",