Remove Entwine inspector (fixes #768)

It never was of great help, and it's quite a hidden feature:
Only available via a keyboard shortcut, and not even
documented in https://github.com/hafriedlander/jquery.entwine.
So I doubt many devs will miss it.

The keyboard shortcut conflicts with emojis on OSX.

Also removing leaktools.js, there's much better ways
to detect javascript memory leaks in browsers these days.

code/LeftAndMain.php

@@ -693,12 +693,6 @@ protected function init()
             Requirements::javascript('silverstripe/admin: client/dist/js/LeftAndMain.Ping.js');
         }
 
-        if (Director::isDev()) {
-            // TODO Confuses jQuery.ondemand through document.write()
-            Requirements::javascript('silverstripe/admin: thirdparty/jquery-entwine/src/jquery.entwine.inspector.js');
-            Requirements::javascript('silverstripe/admin: client/dist/js/leaktools.js');
-        }
-
         // Custom requirements
         $extraJs = $this->config()->get('extra_requirements_javascript');
 

webpack.config.js

@@ -22,7 +22,6 @@ const config = [
       vendor: `${PATHS.SRC}/bundles/vendor.js`,
       // legacy scripts
       'LeftAndMain.Ping': `${PATHS.LEGACY_SRC}/LeftAndMain.Ping.js`,
-      leaktools: `${PATHS.LEGACY_SRC}/leaktools.js`,
       MemberImportForm: `${PATHS.LEGACY_SRC}/MemberImportForm.js`,
       // For IE version 10 and below. These browsers doesn't handle large
       // resource files so need to break browser detection and warning code into

yarn.lock

@@ -679,8 +679,6 @@ apollo-utilities@1.0.21, apollo-utilities@^1.0.0, apollo-utilities@^1.0.21, apol
 append-transform@^0.4.0:
   version "0.4.0"
   resolved "https://registry.yarnpkg.com/append-transform/-/append-transform-0.4.0.tgz#d76ebf8ca94d276e247a36bad44a4b74ab611991"
-  dependencies:
-    default-require-extensions "^1.0.0"
 
 aproba@^1.0.3, aproba@^1.1.1, aproba@^1.1.2, aproba@~1.2.0:
   version "1.2.0"
@@ -2990,12 +2988,6 @@ deep-is@~0.1.3:
   version "0.1.3"
   resolved "https://registry.yarnpkg.com/deep-is/-/deep-is-0.1.3.tgz#b369d6fb5dbc13eecf524f91b070feedc357cf34"
 
-default-require-extensions@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/default-require-extensions/-/default-require-extensions-1.0.0.tgz#f37ea15d3e13ffd9b437d33e1a75b5fb97874cb8"
-  dependencies:
-    strip-bom "^2.0.0"
-
 defaults@^1.0.3:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/defaults/-/defaults-1.0.3.tgz#c656051e9817d9ff08ed881477f3fe4019f3ef7d"