56081 [web] Implement defaultTargetPlatform MacOS/iOS for web. (cla: yes)

56084 Step 1 of 3: Add opt-in fixing Dialog border radius to match Material Spec (a: fidelity, a: quality, cla: yes, f: material design, framework, waiting for tree to go green)

56089 Redirect stdout/stderr in Windows template (cla: yes)

56090 Step 1 of 3: Add opt-in for debugCheckHasMaterialLocalizations assertion on TextField (a: internationalization, a: text input, cla: yes, f: material design, framework, waiting for tree to go green)

56091 Ensure *_kn.arb files are properly escaped with gen_localizations (a: internationalization, cla: yes, f: cupertino, f: material design, framework)