Sync loader between Sentry <-> monorepo

[AbhiPrasad]

JS monorepo loader -> Sentry loader

### Tasks
- [ ] https://github.com/getsentry/sentry/pull/43880
- [ ] https://github.com/getsentry/sentry-javascript/pull/7001
- [ ] https://github.com/getsentry/getsentry/pull/9483

diff --git a/packages/browser/src/loader.js b/packages/browser/src/loader.js
index a914137f6..e1e413971 100644
--- a/packages/browser/src/loader.js
+++ b/packages/browser/src/loader.js
@@ -1,6 +1,4 @@
-// prettier-ignore
-// Prettier disabled due to trailing comma not working in IE10/11
-(function(
+{% load sentry_helpers %}(function(
   _window,
   _document,
   _script,
@@ -31,8 +29,8 @@
     // content.p = promise rejection
     // content.f = function call the Sentry
     if (
-      ('e' in content ||
-        'p' in content ||
+      (content.e ||
+        content.p ||
         (content.f && content.f.indexOf('capture') > -1) ||
         (content.f && content.f.indexOf('showReportDialog') > -1)) &&
       lazy
@@ -58,10 +56,10 @@
     // come out in the wrong order. Because of that we don't need async=1 as GA does.
     // it was probably(?) a legacy behavior that they left to not modify few years old snippet
     // https://www.html5rocks.com/en/tutorials/speed/script-loading/
-    var _currentScriptTag = _document.scripts[0];
+    var _currentScriptTag = _document.getElementsByTagName(_script)[0];
     var _newScriptTag = _document.createElement(_script);
     _newScriptTag.src = _sdkBundleUrl;
-    _newScriptTag.setAttribute('crossorigin', 'anonymous');
+    _newScriptTag.crossOrigin = 'anonymous';
 
     // Once our SDK is loaded
     _newScriptTag.addEventListener('load', function() {
@@ -70,9 +68,6 @@
         _window[_onerror] = _oldOnerror;
         _window[_onunhandledrejection] = _oldOnunhandledrejection;
 
-        // Add loader as SDK source
-        _window.SENTRY_SDK_SOURCE = 'loader';
-
         var SDK = _window[_namespace];
 
         var oldInit = SDK.init;
@@ -142,9 +137,9 @@
 
       // And now capture all previously caught exceptions
       for (var i = 0; i < data.length; i++) {
-        if ('e' in data[i] && tracekitErrorHandler) {
+        if (data[i].e && tracekitErrorHandler) {
           tracekitErrorHandler.apply(_window, data[i].e);
-        } else if ('p' in data[i] && tracekitUnhandledRejectionHandler) {
+        } else if (data[i].p && tracekitUnhandledRejectionHandler) {
           tracekitUnhandledRejectionHandler.apply(_window, [data[i].p]);
         }
       }
@@ -203,9 +198,9 @@
 
   // Do the same store/queue/call operations for `onunhandledrejection` event
   var _oldOnunhandledrejection = _window[_onunhandledrejection];
-  _window[_onunhandledrejection] = function(e) {
+  _window[_onunhandledrejection] = function(exception) {
     queue({
-      p: 'reason' in e ? e.reason : 'detail' in e && 'reason' in e.detail ? e.detail.reason : e
+      p: exception.reason
     });
     if (_oldOnunhandledrejection) _oldOnunhandledrejection.apply(_window, arguments);
   };
@@ -215,6 +210,4 @@
       injectSdk(onLoadCallbacks);
     });
   }
-})(window, document, 'script', 'onerror', 'onunhandledrejection', 'Sentry', 'loader.js', '../../build/bundles/bundle.js', {
-  dsn: 'https://public@example.com/1'
-});
+})(window, document, 'script', 'onerror', 'onunhandledrejection', 'Sentry', '{{ publicKey|safe }}', '{{ jsSdkUrl|safe }}', {{ config|to_json|safe }});

[AbhiPrasad]

Deployed so closing