Add settings for fixed-width tabs (#181729)

* Add settings for fixed-width tabs

This is meant at least partially to address #40290 and
is a continuation of the unfinished work from #40750.

* Only apply fixed width when the setting is on

* Implement chrome-like tab width behavior

Tabs shrink uniformly (down to a limit) but stay fixed-width
when the mouse is over the tab bar.

* Rename width setting to max width

* Make the ifs more readable

* Have event handlers only if the option is set

* 🎨

* Handle sizing artifacts present with wrapping tabs

To achieve this, it's best to remove the transition delay.

* Rename setting to apply only for fixed-sized tabs

* Set default fixed max tab width to 160px

* Minor code tweaks from review comments

* formatting

Co-authored-by: Benjamin Pasero <benjamin.pasero@gmail.com>

* Use disposable listeners

* Remove redundant check for last-in-row

* Apply fade gradient from shrink tabSizing to fixed

* Trying to make the code cleaner and understandable

* Remove transition

On advice of @bpasero, removed transition because
the editor doesn't really use transition that much.

* some cleanup

* fix typo

* Simplify workaround for the overflow issue

* 💄

* 💄

* Let the tabs fix their width before closing the editor

* 💄

---------

Co-authored-by: Benjamin Pasero <benjamin.pasero@microsoft.com>
Co-authored-by: Benjamin Pasero <benjamin.pasero@gmail.com>

build/lib/stylelint/vscode-known-variables.json

@@ -692,6 +692,8 @@
 		"--tab-border-top-color",
 		"--tab-dirty-border-top-color",
 		"--tabs-border-bottom-color",
+		"--tab-sizing-current-width",
+		"--tab-sizing-fixed-max-width",
 		"--testMessageDecorationFontFamily",
 		"--testMessageDecorationFontSize",
 		"--title-border-bottom-color",