Auto merge of #21881 - pyfisch:keyboard-types, r=paulrouget

Use keyboard-types crate

Have embedders send DOM keys to servo and use a strongly typed KeyboardEvent
from the W3C UI Events spec. All keyboard handling now uses the new types.

Introduce a ShortcutMatcher to recognize key bindings. Shortcuts are now
recognized in a uniform way.

Updated the winit port.
Updated webdriver integration.

part of #20331

What this PR does:

* allow the use non-ASCII keyboards for text input
* decouple keyboard event "key" from "code" (key meaning vs location)

What this PR does not do:

* completely improve keyboard events send from winit and webdriver
* add support for CompositionEvent or IME

Notes:

* The winit embedder does not send keyup events for printable keys (this is a regression)
* keyboard-types is on crates.io because I believe it to be useful outside of servo. If you prefer I can add a copy in this repo.

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components/script_traits/Cargo.toml

@@ -20,6 +20,7 @@ gfx_traits = {path = "../gfx_traits"}
 hyper = "0.10"
 hyper_serde = "0.8"
 ipc-channel = "0.11"
+keyboard-types = {version = "0.4.2-servo", features = ["serde"]}
 libc = "0.2"
 malloc_size_of = { path = "../malloc_size_of" }
 malloc_size_of_derive = { path = "../malloc_size_of_derive" }