One approach to getting all scripts and styles cache-busted

cache-bust-frontend-scripts-and-styles.php

<?php

define( 'ASSET_CACHE_INCREMENTOR', 'cachekey-' . time() ); // Source this from anywhere.

add_action( 'wp_enqueue_scripts', function() {
	$assets = array_merge(
		wp_scripts()->registered,
		wp_styles()->registered
	);
	$core_version = get_bloginfo( 'version' );
	foreach ( $assets as $asset ) {
		if ( empty( $asset->ver ) ) {
			$asset->ver = $core_version;
		}
		$asset->ver .= '-' . ASSET_CACHE_INCREMENTOR;
	}
}, 1000 );