`.color` is no longer nullable. Use an empty string instead of null

Part of #74250

- Extend `Disposable` in classes where it makes sense
- Use `DisposableStore` for lists of disposables
- Make `combinedDisposable` take arguments instead of an array (so that you can't pass in an array and then modify the array after the fact)

The widget is better equipped to know when it is visible or not.

#60565

We compile using the alwaysStrict flag so these directives are not needed

This reverts commit 88603b37.

* electron@2.0.0-beta-1

* Update distro

* Update electron.d.ts to 2.0.0-beta.1

* Disable asar as it causes a native crash

* Adopt Module._resolveLookupPaths ASAR patch

* electron 2.x - restore inspector URL in extension host

* electron 2.x - adopt context menu callback for onHide

* electron 2.x - remove workaround for https://github.com/electron/electron/issues/10442

* electron 2.x - update node.d.ts

* electron 2.x - update node.d.ts to 8.9.x

* electron 2.x - keep node.d.ts changes to a minimum

* electron 2.x - remove workaround for https://github.com/electron/electron/issues/10862

* electron 2.x - bump to 2.0.0-beta2

* bump to 2.0.0-beta.3

* Context menu: selecting "Rename" does not put focs into rename box (fix #45601)

* quality "exploration" for easier testing

* empty commit

* push a workaround for #45700

* Certain themes show UI artifacts over activity bar icons (fixes #45700)

* better fix for #45700

* bump to 2.0.0-beta.4

* another fix to prevent flickering for #45700

* avoid remote access in index.js

* bump distro commit

* electron 2.x - do not use --debug anymore

* bump electron to 2.0.0-beta.5

* electron 2.x - add libgtk-3-dev as build dependency for Linux 64

* electron 2.x - workaround freeze on linux on startup

* bump local storage telemetry key

* electron 2.x - do a one time backup of local storage

* enable ELECTRON_ENABLE_LOGGING on macOS at least

* 2.0.0-beta.6

* Fix ctrl+shift+e not focusing explorer on Linux

* distro - use GH electron builds for now

From: https://github.com/Microsoft/TypeScript/issues/15352

TS 2.3.1 introduced a breaking change by [switching to covariant types for callbacks](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#covariance-in-callback-parameters). This change tries to fix these compiler errors in the workbench codebase