This reverts commit ad7e861d.

Fixes #3068

This commit adds the --user-data-dir argument which allows a custom data dir
for Chromium's user data. This is useful when running as root on Linux since
the root user does not have read or write permissions for the ~/.config/Code
dir.

Part of #3068

Linux update notifications

when printing commands for keybindings, skip those that declare arguments and those that start with `vscode.', fixes #4915.

Joh/webview

Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range. (fixes #5004)

fixes #4400

This also changes the behavior of the bin command to find cli.js relatively,
meaning the CLI now supports non-standard install locations.