Add configurable pod log directory cleanup behavior

[jfzunigac]

Summary

Problem (Why)

The current pod log directory cleanup behavior is relies on creating dot files for external cleanup processes. This PR introduces a new configuration option to enable direct automatic cleanup of pod log directories when pods are deleted.

Solution (What + How)

• Added a new optional boolean configuration enablePodLogDirectoryCleanup to the KubeConfig Thrift struct and corresponding config parsing.
• Updated LogStreamManager to conditionally delete pod log directories directly if the new config is enabled, otherwise fallback to creating a tombstone file.
• Added new metric to track pod directory deletions.

Test Plan

• Added testPodDirectoryDeletion unit test to verify pod directory is deleted directly and no dot file is created when the new config is enabled.