Overview

Remove the remaining non-manager users of the old mutators so ticket 7 can delete them. Part of SERVER-136037.

Scope of Work

• page_decryptor.cpp: seed a prebuilt SLSKeystore instead of calling put.
• sls_encryptor_manager_test_fixture.h and the encryption unit tests (sls_kek_storage_api_wt_test.cpp, sls_log_encryptor_manager_*_test.cpp, sls_phylog_decryptor_test.cpp, sls_oplog_decryptor_test.cpp, sls_key_management_commands_test.cpp): replace direct mutator calls with a helper that builds and commits an SLSKeystore.

Acceptance Criteria

• No code outside the store implementation calls the old accessors/mutators, except call sites owned by tickets 3-5.
• All encryption unit tests pass.

Technical Notes

• Largest ticket by line count (test churn), but mechanical.