Untitled, Mode, Text Resource Properties, Commands, Theme

Coalesce has the correct return type of `T[]`. Filter may return `(T | undefined)[]`

* remove more TPromise (for #53526)

* fix failing webview integration tests on macOS

* do not instantiate TPromise (fix #62716)

* more TPromise removal and fixes

* 💄

* 💄

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

This part removes most `use strict` directives that are right after the file header

- avoid public modifier
- use Disposable where applicable
- fix some event handler leaks
- clean up some TODO@ben

This reverts commit 27256832 which turns out did not break the import of vs/nls

This reverts commit 7de696a2.

Seems to have broken loading vs/nls in at least one case in insiders

Don't use this import form in places where it is not needed. This prevents us from correctly detecting duplicate imports

There are many places in the code that do `import Event, { ...} from '.../event'`.

* fix spelling of 'iff' and 'idenifier'

* Keep 'iff' in comment if it means *if and only if*

This change adds a new configuration setting that sets the default
language mode of new untitled files created with Ctrl+N
(workbench.action.files.newUntitledFile).  This activates the user's
desired language mode when a new untitled file is created.

Fixes #8729.

Part of #14067