Content blocks are not pinned to a specific revision

Problem/Motivation

Note: this is not a Panelizer issue, but the problem does manifest itself easily via panelizer.

When a panelized node allows forward revisions (workflow) you expect that changes to a forward revision wont affect the published revision.

Setup:
1. Create a content type which is panlized.
2. Make sure the content type is using workbench moderation. (Draft --> Published)
3. Create a custom content block entity. Mine is a simple text block (title and body)

Bug:
1. Create a new node from the panelized content type and save in draft.
2. Add a text block to the node and add the text "Test1" to the content of the block.
3. Save panelizer.
4. Transition the node to published and notice that the node is published and it displays "Test 1"
5. Create a new draft (forward revision) of the node.
6. In the draft edit the text block and change the text to "Test2".
7. Save panelizer.
8. Navigate back to the published revision and notice the text is "Test2"

Desired solution:
Step 8. Navigate back to the published revision and notice the text is still "Test1"

Proposed resolution

Store block revision id in the panelizer field storage and load blocks using the revision id.