Test coverage for Rust compaction from Java

[patchwork01]

Background

Split from:

• Accelerated compaction support #1359

Depends on:

• Incremental build caching for Rust code in GitHub Actions #2864

Description

We'd like to add any missing test coverage for the linked issue, and ensure it's tested in the GitHub Actions workflows.

Analysis

The compaction-rust module currently has no tests.

Most of the Rust code is untested, except for quantiles.rs in the rust_sketch module.

A number of test files in the Java compaction-runner module are named to refer to a class that has been renamed, i.e. CompactSortedFiles has been renamed to CompactionRunner.

The test helper for instantiating CompactSortedFiles has been changed to create a DefaultSelector object, which could be hidden as an implementation detail for the purposes of tests. These tests can work against CompactionRunner, and the compaction selector could just exist in the test helper.

We could extend the tests against CompactionRunner to also test with Rust. We could add coverage for the logic in DefaultSelector. We could test any usage of the methods on the CompactionRunnerDetails interface, and remove any that are not needed.