Context

This MR fixes the baker test framework for Mumbai and Alpha following the changes of !7516 (merged)

Manually testing the MR

Ensure that dune exec src/proto_016_PtMumbai/lib_delegate/test/main.exe and dune exec src/proto_alpha/lib_delegate/test/main.exe succeed

n/a Document the interface of any function added or modified (see the coding guidelines)
n/a Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
n/a 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).
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