[Jelly] Add jelly colors to Bluetooth config dialog

This change jellifies the Bluetooth pairing dialog, enabling it to
dynamically update the CSS used for the dialog so that it matches the
theme chosen by the user.

Screenshot:
Before Jelly:
https://screenshot.googleplex.com/3rYuUkgn7td7k72.png
https://screenshot.googleplex.com/8o68yahXndD5xeC.png

after jelly
https://screenshot.googleplex.com/4ntWCsRckjSq4uB
https://screenshot.googleplex.com/9TumB8fVPLdRHon.png

video: https://drive.google.com/file/d/1x8tlqnS-hbB37OgIq2UQ0TrM3fJrcb6i/view?usp=sharing

Bug: b:274649523
Test: Deployed locally added unittest
Change-Id: I874ff948c5c2a7dc3a3ba9f1720f9bc446b2a5be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4447308
Reviewed-by: Emily Stark <estark@chromium.org>
Commit-Queue: Theo Johnson-kanu <tjohnsonkanu@google.com>
Reviewed-by: Wes Okuhara <wesokuhara@google.com>
Reviewed-by: Chad Duffin <chadduffin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1134185}