Driver warns that spark.executor.memoryOverhead is unset when spark.executor.memoryOverheadFactor is set, and in local mode #6189

Describe the bug

CometDriverPlugin.warnIfExecutorMemoryOverheadUnset warns whenever spark.executor.memoryOverhead is not set (Plugins.scala#L165-L180). For large executors, the tuning guide recommends raising spark.executor.memoryOverheadFactor instead (tuning.md#L177-L184). Users who follow that advice are still told to set spark.executor.memoryOverhead.

The warning also fires in local mode, where there is no container to size. The native memory usage log already skips local mode.

Steps to reproduce

Start an application with the Comet plugin, off-heap memory enabled, spark.executor.memoryOverheadFactor=0.2 and no spark.executor.memoryOverhead. The driver logs "spark.executor.memoryOverhead is not set".

Expected behavior

No warning when the overhead is configured through spark.executor.memoryOverheadFactor or spark.kubernetes.memoryOverheadFactor, or when the master is local.