Revert "Clean up HTML and CSS for desktop Reader Mode settings dialog."

This reverts commit dcb2725711d7d98423b803c23c5394d6da5de17a.

Reason for revert: Suspecting this CL as cause of failures in https://ci.chromium.org/p/chromium/builders/ci/ios-slimnav/10089

The failing test is ReadingListTestCase/testSavingToReadingListAndLoadDistilled

And the error message seems to be about the UI, so this CL might've broke this test.

Will reland if it's not the cause.

Original change's description:
> Clean up HTML and CSS for desktop Reader Mode settings dialog.
> 
> The main goal of the CL is to separate the desktop-specific HTML from
> the shared HTML to make testing more straightforward.
> 
> Since this was already a refactoring CL, I also applied the fixes
> surfaced by the presubmit checks.
> 
> Bug: 952034
> Change-Id: I963dff8ef49ef3b78b585aa2040876953a2de004
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1925688
> Commit-Queue: Aran Gilman <gilmanmh@google.com>
> Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#717963}

TBR=mdjones@chromium.org,wychen@chromium.org,gilmanmh@google.com

Change-Id: If1d2ec038244584665c362badbdfe9ffa0e19c93
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 952034
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930288
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718024}
13 files changed