Proto/Test: don't reference Alpha protocol in the code

Context

References to Tezos_raw_protocol_alpha, Tezos_protocol_alpha and Tezos_protocol_alpha_parameters fail to compile after protocol snapshotting. Open required modules via parameters in dune files instead.

Most of the changes seem to be introduced by the merge of Tenderbake branch !3738 (merged).

Manually testing the MR

Snapshot and compile

$ ./scripts/snapshot_alpha_and_link.sh 012 idiazabal
$ make

This was failing before the change, now succeeds.

...
File "src/proto_012_PscUUfM2/lib_plugin/test/test_consensus_filter.ml", line 28, characters 5-48:
28 | open Tezos_protocol_alpha.Protocol.Alpha_context
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: Unbound module Tezos_protocol_alpha
...