integration tests cleanup (#880)

* add: test-util feature to s3 integration test Cargo.toml

* add: test-util feature to integration tests missing it
remove: vestigial src/lib.rs files
sort: integration test deps

* fix: copy-paste error in Cargo.toml

* fix: copy-paste error in Cargo.toml

* verify: integration tests run without lib files
fix: outdated dependency path name
remove: extra space in Cargo.toml

* update: Credential creation method in integration test