proto/receipts: Differentiate bakers rewards from their edge on staker rewards

What

Differentiate bakers rewards from their edge on staker rewards.

Why

Currently both receipts use the same encodings which make them undistinguishable without recomputing actual changes theyr corresponds to.

How

By having two different encodings for balance updates to bakers deposits, one dedicated to baker_own_stake and the other to baker_edge.

Manually testing the MR

Running a node and observing balance updates from block metadata. Otherwise, dune exec src/proto_alpha/lib_protocol/test/pbt/main.exe -- --file test_balance_updates_encoding.ml and dune exec tezt/tests/main.exe -- --file adaptive_issuance.ml both check balance updates.

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