feat(skill&shield): 实现护盾持续时间功能，调整魔法盾冷却

1.  为护盾技能添加duration配置，支持永久/限时护盾
2.  新增护盾倒计时逻辑，到期自动清空护盾
3.  调整英雄6301魔法盾的冷却时间为10秒，新增7秒持续时长配置
4.  重构HeroAttrsComp，新增护盾持续时间字段与清空护盾方法

assets/script/game/common/config/heroSet.ts

@@ -549,7 +549,7 @@ export const HeroInfo: Record<number, heroInfo> = {
                     { lv: 2, s_lv: SkillLv.Lv2, overrides: {"ap":120}, desc: "普通攻击 造成 120% 伤害" },
                 ],
             },
-            6301: { uuid: 6301, name: "魔法盾", lv: 1, cd: 8, ccd: 0, overrides: {"ap":30}, desc: "{target}获得生命最大值{ap}%的护盾",
+            6301: { uuid: 6301, name: "魔法盾", lv: 1, cd: 10, ccd: 0, overrides: {"ap":30}, desc: "{target}获得生命最大值{ap}%的护盾",
                 lv_entries: [
                     { lv: 8, s_lv: SkillLv.Lv2, overrides: {"ap":60}, desc: "{target}获得生命最大值{ap}%的护盾" },
                     { lv: 16, s_lv: SkillLv.Lv3, overrides: {"ap":120}, desc: "{target}获得生命最大值{ap}%的护盾" },