feat: load SPI Service in jvm plugin

[cssxsh]

添加从 插件 jar 中 加载 SPI Service 的API

用来实现统一加载 Command 或者 PluginConfig 之类服务的效果

private val commands: List<Command> by services()

override fun onEnable() {
    for (command in commands) command.register()
}

override fun onDisable() {
    for (command in commands) command.unregister()
}