Cache context ignores request attribute changes

Problem/Motivation

Coming from #3520384: Append views display type to element name:

Lupus CE renderer correctly adds this cache contexts:
'url.query_args:_content_format',
'url.query_args:_select',

But that's apparently not enough, since the content-format can be set via request attribute as well - as done by lupus_decoupled_ce_api.

Steps to reproduce

see ##3520384: Append views display type to element name

Proposed resolution

That means, lupus_ce_renderer should expose this is a new cache context which works like getContentFormatFromRequest() method.

Then we can replace our url.query_args._content_format cache context with the new cache context.