cleanup: cleanup usage of getSecurityManager()

[BradWalker]

cleanup: cleanup usage of getSecurityManager()

desc: getSecurityManager() is deprecated and marked for imminent removal. In addition as of JDK 24, getSecurityManager() returns null.

This change removes getSecurityManager() from various places that have minimal impact.

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[mbien]

some filesystem tests (possibly others too) still rely on the SM to intercept events. Please add the all-tests label and make sure everything is green when you do cleanups across clusters or in core functionality.