DRILL-8446: Incorrect use of OperatingSystemMXBean

[jnturton]

DRILL-8446: Incorrect use of OperatingSystemMXBean

Description

Simplify CpuGaugeSet fixing the non-Sun/Oracle code path in the process.

The com.sun.management internal implementation of OperatingSystemMXBean is used by Drill to report a CPU metric that is not available in the public interface. Even though code to handle non-Sun/Oracle runtimes for the OperatingSystemMXBean was present, it would still cause them to attempt to load a class from com.sun.management causing a NoClassDefFoundError.

Documentation

N/A

Testing

Launch Drill and check the affected gauges in

• OpenJDK 64-Bit Server VM (build 17.0.9+9-Debian-1, mixed mode, sharing)
• IBM J9 VM (build 2.9, JRE 1.8.0 Linux amd64-64-Bit Compressed References 20230817_56476 (JIT enabled, AOT enabled)

[jnturton]

LGTM +1

@jnturton Does this fix the Splunk flaky test?

Hopefully.