Improve options usage

[swissspidy]

Task Description

Look into how these queries can be optimized/avoided, e.g. using wp_prime_option_caches or wp_prime_option_caches_by_group

From Jonny:

	public function get_setting( string $key, $default_value = false ) {
		if ( function_exists('wp_prime_option_caches_by_group') & ! $this->option_loaded ) {
			wp_prime_option_caches_by_group(self::SETTING_GROUP);
			wp_prime_option_caches_by_group(self::SETTING_GROUP_EXPERIMENTS);
			$this->option_loaded = true;
		}