Added RANDOM, RANDOM_HEX snippet variables

Update xterm, support fast scroll, fix xterm element NPEs

Fixes #82581

Fixes #78431

Fixes #82622

Diff: https://github.com/xtermjs/xterm.js/compare/cbb79a7...91cbeec

- API | undefined fixes
- Fast scrolling feature

* Add setting to configure the max memory for tsserver

* Fix silly tpo from fixing formatting

* Add "MB" to setting description string

* Add validation to configuration value

* Add 128MB as a lower bound

* Fix #82199 

This PR resets color theme of number, title and built_in at Preview with light theme.

* Bad whitespace indentation Fixe

* owner comment Removed

Fixes #82619

Webviews cannot be reparented as it destroys their contents

The main VS Code process should not need to know about the default values for `localResourceRoots`. Leave this up to the extension instead

The current implementation is a noop since we've already updated the state when it is invoked

Instead pass over the extension when resolving the extension itself

Diff: https://github.com/xtermjs/xterm.js/compare/84b56b7...cbb79a7

- Tests/doc change
- alt+up/down fix for mac

Add missing preposition

related to #66522