Add an AppData XML data file to Linux builds

remove extendObject #17117

The AppData files provide descriptive data about an application, and is
typically used in application managers to display additional information to
the user. Having an AppData file is especially important for some graphical
application installers: without one, an application manager may not event
show an entry for the application. This happens for example in GNOME Software.

For the sake of completeness, this commit not only adds the AppData file to
the Flatpak build, but also to the Linux .deb and .rpm packages.

fixes #12845

Implement terminal.integrated.cwd

Fixes #17387

Part of #17331

Updates path completions for directories and files to use a file icon instead of the generic icon they currently use.

Fixes #16888

**Bug**
The js/ts completion provide can currently only complete whole words (as defined by `TextDocument.getWordRangeAtPosition`). This causes completion of literal string types to fail if they are not a whole word.

**Fix**
Instead of relaying on the default range, compute a range by taking the longest match of the replacement text from the current position.

Fixes #17232

Add a few niceties for making Flatpak builds of VSCode

Make high contrast detection configurable

Issue with saving files on mounted drive: "Could not resolve any model with provided uri" (fixes #17345)