Change Xcode project developmentRegion to 'en' and plist CFBundleDevelopmentRegion to DEVELOPMENT_LANGUAGE (#34293)

* move flutter_assets to App.framework

* Roll engine to 05fee4eeee0ff6b219b1fcc394371e5f6963cc46

05fee4eee Update default flutter_assets path for iOS embedding (flutter/engine#7518)
02205db01 Roll src/third_party/skia 5d052dac3ac1..02738a86e5fd (4 commits) (flutter/engine#7541)
af907c074 Roll src/third_party/skia 5c7a3ac0e214..5d052dac3ac1 (7 commits) (flutter/engine#7540)
dde286673 IWYU to get SkFontMetrics (flutter/engine#7539)

This reverts commit d8db70af.

* move flutter_assets to App.framework

* remove flutter_assets references from all pbxproj files checked in

For https://github.com/flutter/flutter/issues/24712

This test verifies that https://github.com/flutter/engine/pull/6923 will speedup the average rasterize time of this test from ~150ms to ~10ms

Please see non-auto-generated files in https://github.com/flutter/flutter/pull/25381/commits/37b21d9fb4756a8d8d12ae0def1d0640740c8818