[2.0.0-beta3] Do we keep BlockSource plugin?

Problem/Motivation

Following 🐛 [2.0.0-beta1] Blocks implementing PluginFormInterface don't work with BlockSource Needs review , we still have an issue: blocks from views are not saving their configuration properly.

Because of that and the fact we are "authorizing" only a small subset of blocks, Christian was proposing to remove this source in 2.0 and reintroduce it in 2.1 with a brand new implementation.

Proposed resolution

Let's expose the plan for 2.1, if we all agree about it and if it is not possible to do it in beta2, let's:

1. remove this source (and the related hook) from 2.0
2. create the related ticket for 2.1