fix(lib/vscode): remove native-keymap and keytar

[oxy]

native-keymap is only used in the electron process, so we don't need it.
This allows us to drop our libx11 and libxkbfile build dependencies.

[jsjoeio]

LGTM! Just confused about the native-keymap declaration file if we're removing the dependency

[oxy]

Update: I spent the day investigating keytar, which initially was a much scarier dep to remove, but also allows us to drop our dependency on libsecret-dev, which means CI no longer needs to pull in any desktop-specific Linux packages! 🎉

I put that change in this PR too, since it felt like the logical thing to do (they touch nearly the same lines in the Dockerfiles, which means that if I made two PRs, one would have to be rebased and have conflicts resolved).

There's some scarier stuff going on with how keytar is used in vscode, but it's not an issue to drop it:

keytar is provided for extensions to be able to use the operating system keyring (when running natively) to store password secrets. To make this work, VSCode actually has a hook on require that replaces require('keytar') in an extension with a RPC-like system that shares the same API, but is proxied elsewhere deep inside.

For the web, VSCode already includes class LocalStorageCredentialsProvider implements ICredentialsProvider which stores them in a JSON in local storage, and provides a keytar-esque API.

I've tested this by writing a custom VSCode extension that uses "keytar" injected by vscode to set credentials, and it successfully stores them in LocalStorage. I also tested against GH Codespaces, which shows the same behavior.

I've also added notes to the lib/vscode/src/typings files to indicate why I pulled them in.

[oxy]

Note for review: @types/keytar is deprecated since keytar includes types - I removed both and added a typings file.

[jsjoeio]

Woo! Great work and thanks for adding great comments for future us!

Ship it!