Can't use VBO views on the My Workbench page

Problem/Motivation

In trying to add a view to the My Workbench landing page, I discovered said views cannot contain bulk operations... because the output of all blocks is rendered and placed in #markup. The problem with this is that output is passed through Xss::filterAdmin()... removing any form tags.

Proposed resolution

Blocks have built as render arrays and we're returning a render array. Why don't we just return the blocks in the render array?

Remaining tasks

Review incoming patch and decide if it's a good way forward (with minimal other changes).

User interface changes

N/A

API changes

None

Data model changes

N/A