Mark TR_J9VMServer virtual methods with override

[cjjdespres]

The isIndexableDataAdrPresent() and isOffHeapAlocationEnabled() methods override the TR_J9VMBase implementations. They are now marked with override; a compilation error results without it with clang in the default configuration (with -Werror).

[cjjdespres]

Attn @mpirvu

[mpirvu]

jenkins test sanity zlinuxjit,xlinuxjit jdk17

[mpirvu]

xlinuxjit had a timeout on jdk_util_0 zlinuxjit had a test assert failure on the same test

jdk_util_0 Start Time: Sat Oct 19 20:19:55 2024 Epoch Time (ms): 1729383595298
20:19:55  variation: -Xdump:system:none -Xdump:heap:none -Xdump:system:events=gpf+abort+traceassert+corruptcache Mode150
20:19:55  JVM_OPTIONS: -XX:+UseJITServer -Xdump:system:none -Xdump:heap:none -Xdump:system:events=gpf+abort+traceassert+corruptcache -XX:+UseCompressedOops -Xverbosegclog 
............
20:30:32  ACTION: main -- Failed. Execution failed: `main' threw exception: java.lang.AssertionError: Some tests failed
20:30:32  REASON: Assumed action based on file name: run main DeflateIn_InflateOut 

[cjjdespres]

The xlinuxjit failure was in CountLargeTest, which has had timeouts in the past (https://github.com/eclipse-openj9/openj9/issues/15198), including one that was JITServer-specific (https://github.com/eclipse-openj9/openj9/issues/17971, on aarch64). The zlinuxjit failure in DeflateIn_InflateOut I haven't seen before. Unfortunately, that latter test component is one of those that merely reports its overall success or failure in the logs without other detail. I can double-check the nightly tests to see if either has occurred there.

I don't think the override specifier addition is responsible - I'm fairly sure that it just asserts that the virtual method does in fact override something, and doesn't influence anything else.

[mpirvu]

I agree that the changes in this PR are very unlikely to cause the issues seen in testing.