migrate Iterable<> to Stream<>

they are everywhere and are a remnant of when we had to fake streams with Guava in Java 7

Start by locating all uses of Iterable<> and Stream<> across the Java codebase and identify the Guava-based stream compatibility they replace. Review the surrounding APIs before changing types, then run the repository's available tests and build checks. Done means the outdated Iterable<> usage has been migrated consistently without breaking callers or tests.

Written by the indexing model from the issue text.