This reverts commit 9333b7c1.

Queries the system list of user-preferred languages, and sends it to the
engine just after starting it up.

Windows portion of https://github.com/flutter/flutter/issues/45152

Relands https://github.com/flutter/engine/pull/20399

Makes BinaryMessenger available from FlutterEngine, rather than just the plugin registrar. This allows for method channels directly in applications without building them as plugins, and matches the other platforms.

Requires some restructuring of code and GN targets in the client wrappers to make the internals in the shared section usable by the implementations of platform-specific parts of the wrappers. Also fixes a latent issue with EnableInputBlocking symbols being declared but not defined for Windows that came up during testing of the restructing.

Fixes https://github.com/flutter/flutter/issues/62871

This reverts commit 7fa21a45.

Makes BinaryMessenger available from FlutterEngine, rather than just the plugin registrar. This allows for method channels directly in applications without building them as plugins, and matches the other platforms.

Requires some restructuring of code and GN targets in the client wrappers to make the internals in the shared section usable by the implementations of platform-specific parts of the wrappers. Also fixes a latent issue with EnableInputBlocking symbols being declared but not defined for Windows that came up during testing of the restructuring.

Fixes https://github.com/flutter/flutter/issues/62871

FlutterViewControllers.

Reland #19396 with a fix for improper scale that was affecting internal tests

Tested: Ran all unittests, ran internal tests, and ran workstation on Fuchsia
BUG: 53062, 53063

* Handle glfwGetPrimaryMonitor returning nullptr

[glfwGetPrimaryMonitor](https://www.glfw.org/docs/3.3/group__monitor.html#ga721867d84c6d18d6790d64d2847ca0b1) may return NULL in non-error cases when no monitor is found. This started to happen recently with an update to the linux distribution, see internal b/162545223.

Handling this case avoids a crash and instead assumes a pixel density.

controllers instead of views.

* Make sure ios tests fail if they fail

* explain

hasStrings message for checking for pasteable clipboard contents without actually reading them, for iOS14 clipboard alerts.

A recent refactoring broke the USE_LEGACY_ENCODABLE_VALUE codepath in
standard_codec.cc, which went unnoticed since it wasn't being compiled.
This fixes the breakage, and also adds a temporary minimal unit test
target that ensures that all the USE_LEGACY_ENCODABLE_VALUE paths are
being compiled.