function trimCacheAll(node) {
    if (node.num === 0) return // 0 = infinite, so no need to trim
    Object.keys(node.cache).forEach( (key) => {
        const msgs = node.cache[key]
        // See if the array is now too long - if so, slice it down to size
        if ( msgs.length > node.num ) {
            node.cache[key] = msgs.slice( msgs.length - node.num )
        }
    })

    // Save the cache
    node.setC(node.varName, node.cache, node.storeName)
}
Trim all of the cache to the requested number of entries
@param {runtimeNode & cacheNode} node Reference to node instance