fix: resolve ErrorProne StringSplitter warnings

[franvila]

Type of change

• Refactoring

Description

Replace all String.split(regex) and Pattern.split(input) calls with their two-argument form passing -1 as the limit. This makes the splitting behavior explicit by preserving trailing empty strings, which is what ErrorProne's StringSplitter check requires.

This resolves all 22 StringSplitter warnings across 10 files without introducing Guava's Splitter or adding @SuppressWarnings annotations.

Affected modules:

• kroxylicious-runtime (HostPort)
• kroxylicious-openmessaging-benchmarks (RunMetadata, ResultComparatorTest)
• kroxylicious-integration-tests (ExpositionIT, ProxyProtocolIT, RoutingContextContractIT, SaslTerminationOauthBearerIT, AbstractAuthzEquivalenceIT, AuthzIT)
• kroxylicious-systemtests (Environment, Exec, DeploymentUtils, KafkaVersionUtils)

Additional Context

The String.split(String) method silently discards trailing empty strings, which can lead to surprising behavior. Passing -1 as the limit makes the behavior explicit and predictable. See https://errorprone.info/bugpattern/StringSplitter.

Checklist

• New tests written (where applicable).
• If making a user-facing change, documentation is provided, or if the intent is to provide documentation in a follow up PR, an issue is raised tracking the need for the documentation update. Link the to issue in this checklist.
• Existing unit/integration/system tests passing.
• Any Sonarcloud warnings are addressed (or suppressed with @SuppressWarnings and a justifying comment).
• PR references related GitHub issue(s) so they are closed on merging.
• If AI tools assisted with code changes, ensure commit messages include Assisted-by: trailer (see DEV_GUIDE.md).
• For user facing changes, add a logchange entry YAML file to changelog/unreleased/ (remember to include changes affecting the API of the test artefacts too). See DEV_GUIDE.md for the entry format.

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