[fix][sec] Upgrade zstd-jni to 1.5.7-20 - #26766

Motivation

Update zstd-jni beyond 1.5.7-15 to include upstream maintenance fixes. Pulsar directly uses this dependency in compression interoperability tests; its production ZSTD codec uses Airlift.

Modifications

Upgrade zstd-jni from 1.5.7-15 to 1.5.7-20. The new release is a multi-release jar: Java 17/21 retain JNI implementations, while Java 22+ can select the FFM implementations provided by the library.

Verifying this change

• Make sure that the change passes the CI checks.

help assemble sanityCheck checkBinaryLicense passed with configuration cache enabled, including Checkstyle/Spotless. All 51 cases in CompressorCodecBackwardCompatTest and CompressorCodecTest passed on both Java 17 and Java 25 with retries disabled and no skips. These cover Pulsar's codec interoperability; they are not exhaustive coverage of the library's new FFM APIs.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment