Baker: aggregated operations retrival from block content fix

What

Fixes the following behavior : when reproposing, the baker doesn't consider aggregated operations when retrieving consensus operations from the latest block content.

Why

In a situation where such aggregated operations contains operations that are not in the node/baker mempool, such operations are not included in a reproposed block.

How

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR