Moving styles from the existing styles to common/layout
or components stylesheets they should be associated with.
Components are identified using PascalCase. Lowercase names are used for things
that are not components. This distinction should help us reason with the code
better and make it clearer where CSS belongs, saving us lots of wasted
effort discussing conventions.
Patch isn't making actual CSS changes themselves - for testing purposes this
should be a NOOP.
In preparation for the gradient removal,
'background-gradient.less' is marked as legacy.
Merged 'externalLinks.less' into content.less, they belong to content.
Bug: T249073
Change-Id: I8dbc29b7a19f7613b57b0984a8befaeae9c08798
