Enhance Event Emitter to ignore events generated by same process ID

[t1m0thyj]

Is your feature or enhancement request related to a problem or limitation? Please describe

As a developer of a Zowe app like Zowe Explorer that uses the Imperative event emitter, I register the ON_VAULT_CHANGED event because I want to know when an external app has updated credentials. The event also fires when my own app has updated credentials, which is not ideal as it may result in a duplicate refresh operation (e.g. the "Update Credentials" dialog shows twice).

Describe your enhancement idea

Add an ignoreSameProcess option when registering to watch for an event, which checks the PID (process ID) of the event and prevents events from being emitted to the same app that triggered them.

Describe alternatives you've considered

An alternative workaround is for apps like ZE to modify the EventProcessor prototype to skip duplicate events, but this is kind of hacky:

const oldEmitZoweEvent = (imperative.EventProcessor.prototype as any).emitZoweEvent;
(imperative.EventProcessor.prototype as any).emitZoweEvent = function (eventName: string): void {
    if (eventName === imperative.ZoweUserEvents.ON_VAULT_CHANGED) {
        Constants.IGNORE_VAULT_CHANGE = true;
    }
    oldEmitZoweEvent.call(this, eventName);
};
imperative.EventOperator.getWatcher().subscribeUser(imperative.ZoweUserEvents.ON_VAULT_CHANGED, async () => {
    if (Constants.IGNORE_VAULT_CHANGE) {
        Constants.IGNORE_VAULT_CHANGE = false;
        return;
    }
    // Handle event here
});

Provide any additional context

Related to this Zowe Explorer PR: zowe/zowe-explorer-vscode#3157

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