[JetBrains] Custom global key handler supporting Enter/Delete/Backspace and Enter+Shift in all IntelliJ IDEs flavors in the uniform way

[PiotrKarczmarz]

CLOSE https://linear.app/sourcegraph/issue/CODY-4704/backspace-and-enter-keys-not-working-in-rider-cody-window-macos

Special global handler for Backspace, Delete, Enter, and Shift+Enter which are not working properly in the CEF instance in Rider and potentially in other IntelliJ IDEs flavors. Even, when there are no shortcuts defined for these keys in the current keymap, press key events still aren't forwarded to the CEF instance, but looks like they are swallowed by other dispatchers (DefaultKeyboardFocusManager.keyEventDispatcher) in the pipeline:

The implementation un-consume a key event (via reflection), already consumed by other dispatchers, which allow a key event to be later handled by Cef component (webview).

Detecting the event source using JBCefOsrComponent type, which is about 30% faster than calling browser.uiComponent.hasFocus(), 2080.00 ns. vs 2923.53 ns. on average (handler is called for every keystroke, but the execution is narrowed only for JBCefOsrComponent to make minimal performance impact on IDE UI.

Test plan

1. Run Rider
2. Check if modifier keys are working in the Cody tool window:
   • Enter
   • Delete
   • Backspace
   • Enter + Shift

[pkukielka]

LGTM