The My Account page was written with legacy configforms styling in

mind. We worked around layout issues with custom styling, dynamically

altering some classes, and trying to make some parts of the UI line up

and blend together in somewhat hacky ways.
Djblets 2.0 switches configform pages over to a cleaner, more modern CSS

Component structure, with improved styling and layout. This definitely

breaks a lot of the My Account page, which this change fixes by

utilizing the new layout constructs and stripping away old hacks.
For the most part, this includes wrapping some elements in a

djblets-l-config-forms-container container element, switching to newer

class names, and removing unwanted styling to allow some of the fixes in

the core classes to work correctly.
There are a couple cases where we've had to alter some CSS to work

correctly in modern configforms. For instance, rb-c-search-input and

rb-c-form-field__errors needed to work around configforms taking

precedence and overriding some styling. These are unfortunate hacks,

currently. The plan, a bit further down the road, is to centralize our

styling in a more common component, but for now this is a necessary

evil.

Unit tests pass.
Tested every subpage and form in the My Account page.