[JENKINS-37566] - FindBugs - Cleanup issues in ExportTable implementation

[oleg-nenashev]

This pull request just suppresses two issues in ExportTable implementation.

• Caching of stacktrace for heapdumps. No warnings anymore
• Ignore Serialization warnings for ExportList since this class is a part of internal API && is not being actually serialized

For discussion about caching or Source stacktraces:

• It is a legacy behavior introduced by @kohsuke in 5db46de (remoting-2.40).
• For every object Deallocation and Reference Counter Increment Remoting calculates the stacktrace and then also clones it. Implementation in Throwable is provided below
• The current behavior causes calculation and memory overheads, just to make heapdumps to provide more info
• I doubt we want this behavior to be enabled by default

Throwable implemetation:

    public StackTraceElement[] getStackTrace() {
        return getOurStackTrace().clone();
    }

    private synchronized StackTraceElement[] getOurStackTrace() {
        // Initialize stack trace field with information from
        // backtrace if this is the first call to this method
        if (stackTrace == UNASSIGNED_STACK ||
            (stackTrace == null && backtrace != null) /* Out of protocol state */) {
            int depth = getStackTraceDepth();
            stackTrace = new StackTraceElement[depth];
            for (int i=0; i < depth; i++)
                stackTrace[i] = getStackTraceElement(i);
        } else if (stackTrace == null) {
            return UNASSIGNED_STACK;
        }
        return stackTrace;
    }

JENKINS-37566

@reviewbybees

[ghost]

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[jglick]

Just inline again and use @SuppressFBWarnings.

[oleg-nenashev]

@reviewbybees done