Retire first batch of deprecated Bazel migration shims (`//src`, `//memory`)

[4og]

Purpose

Retire the first batch of deprecated Bazel migration shims after updating their consumers to the replacement labels.

Scope

Category	Deprecated targets
Rust source-layout shims	The whole content of //src: //src/containers:containers //src/elementary:elementary //src/log/score_log:score_log //src/log/stdout_logger:stdout_logger //src/log/stdout_logger_cpp_init:stdout_logger_cpp_init //src/sync:sync //src/testing_macros:score_testing_macros //src/thread:thread
String-manipulation shims	//score/memory:{string_literal,string_comparison_adaptor,split_string_view}
Atomic-indirection shims	//score/memory/shared:{atomic_interface,atomic_indirector,atomic_indirector_mock_binding}

Acceptance criteria

• All known consumers use the replacement labels.
• The deprecated aliases/shims and obsolete compatibility headers are removed.
• Affected Bazel build and test targets succeed without dependencies on the removed labels.
• The Epic deprecation inventory (Epic: Retire deprecated Baselibs APIs and Bazel targets #595) is updated to reflect the removals.