Enhance the Vim Mode toggle discoverability (#21589)

Closes https://github.com/zed-industries/zed/issues/21522

This PR adds an info tooltip on the Welcome screen, informing users how
Vim Mode can be toggled on and off. It also adds the Vim Mode toggle in
the Editor Controls menu. This is all so that folks who accidentally
turn it on better know how to turn it off. We're of course already able
to toggle this setting via the command palette, but that may be harder
to reach for beginners. So, maybe that's enough to close the linked
issue? Open to feedback.

(Note: I also added a max-width to the tooltip's label in this PR. I'm
confident that this won't make any tooltip look weird/broken, but if it
does, it may be because of this new property).

| Welcome Page | Editor Controls |
|--------|--------|
| <img width="800" alt="Screenshot 2024-12-05 at 11 20 04"
src="https://github.com/user-attachments/assets/1229f866-6be5-45cd-a6b8-c805f72144a6">
| <img width="800" alt="Screenshot 2024-12-05 at 11 12 15"
src="https://github.com/user-attachments/assets/f082d7f9-7d56-41d1-bc86-c333ad6264c7">
|

Release Notes:

- N/A

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>

assets/icons/info.svg

@@ -0,0 +1,12 @@
+<svg width="14" height="14" viewBox="0 0 14 14" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0_2131_1193)">
+<circle cx="7" cy="7" r="6" stroke="black" stroke-width="1.5"/>
+<path d="M6 10H7M8 10H7M7 10V7.1C7 7.04477 6.95523 7 6.9 7H6" stroke="black" stroke-width="1.5" stroke-linecap="round"/>
+<circle cx="7" cy="4.5" r="1" fill="black"/>
+</g>
+<defs>
+<clipPath id="clip0_2131_1193">
+<rect width="14" height="14" fill="white"/>
+</clipPath>
+</defs>
+</svg>