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-main/spellchecker-spec.ts

@@ -16,7 +16,8 @@ ifdescribe(features.isBuiltinSpellCheckerEnabled())('spellchecker', () => {
       show: false,
       webPreferences: {
         nodeIntegration: true,
-        partition: `unique-spell-${Date.now()}`
+        partition: `unique-spell-${Date.now()}`,
+        contextIsolation: false
       }
     });
     w.webContents.session.setSpellCheckerLanguages(['en-US']);