feat: enable context isolation by default (#26890)

* feat: enable context isolation by default

* chore: set default in ctx iso getter

* spec: make all specs work with the new contextIsolation default

* spec: fix affinity specs

* spec: update tests for new ctx iso default

* spec: update tests for new ctx iso default

* spec: update tests for new ctx iso default

* spec: update tests for new ctx iso default

* chore: move stray prod deps to dev deps

* spec: update tests for new ctx iso default

* turn off contextIsolation for visibility tests

* turn off contextIsolation for <webview> tag nodeintegration attribute loads native modules when navigation happens

Co-authored-by: John Kleinschmidt <jkleinsc@electronjs.org>

spec/fixtures/no-proprietary-codecs.js

@@ -16,7 +16,8 @@ app.whenReady().then(() => {
   window = new BrowserWindow({
     show: false,
     webPreferences: {
-      nodeIntegration: true
+      nodeIntegration: true,
+      contextIsolation: false
     }
   });