proxy_agent: Use proxy-from-env for robustness

Now we support pretty much every variable under the sun along with
$NO_PROXY all correctly and with minimal code on our end.

lib/vscode/package.json

@@ -65,6 +65,7 @@
     "native-watchdog": "1.3.0",
     "node-pty": "0.10.0-beta17",
     "proxy-agent": "^4.0.0",
+    "proxy-from-env": "^1.1.0",
     "rimraf": "^2.2.8",
     "spdlog": "^0.11.1",
     "sudo-prompt": "9.1.1",
@@ -95,6 +96,7 @@
     "@types/minimist": "^1.2.0",
     "@types/mocha": "2.2.39",
     "@types/node": "^12.11.7",
+    "@types/proxy-from-env": "^1.0.1",
     "@types/sinon": "^1.16.36",
     "@types/trusted-types": "^1.0.6",
     "@types/vscode-windows-registry": "^1.0.0",

lib/vscode/yarn.lock

@@ -302,6 +302,13 @@
   resolved "https://registry.yarnpkg.com/@types/node/-/node-13.13.28.tgz#b6d0628b0371d6c629d729c98322de314b640219"
   integrity sha512-EM/qFeRH8ZCD+TlsaIPULyyFm9vOhFIvgskY2JmHbEsWsOPgN+rtjSXrcHGgJpob4Nu17VfO95FKewr0XY7iOQ==
 
+"@types/proxy-from-env@^1.0.1":
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/@types/proxy-from-env/-/proxy-from-env-1.0.1.tgz#b5f3e99230ca4518af196c18267055fc51f892b7"
+  integrity sha512-luG++TFHyS61eKcfkR1CVV6a1GMNXDjtqEQIIfaSHax75xp0HU3SlezjOi1yqubJwrG8e9DeW59n6wTblIDwFg==
+  dependencies:
+    "@types/node" "*"
+
 "@types/semver@^5.4.0", "@types/semver@^5.5.0":
   version "5.5.0"
   resolved "https://registry.yarnpkg.com/@types/semver/-/semver-5.5.0.tgz#146c2a29ee7d3bae4bf2fcb274636e264c813c45"