fix: merge plugin config when load because of plugin preset

[noahziheng]

之前在 Scan 阶段预处理的 pluginConfig，存在边界 case：

• 插件合集 a 内 default 启用了插件 b
• app 在 prod 环境未启用插件合集 a
• 但预处理过程中把全部 default 合并，全部 prod 合并
• 预期应为 prod 是 a 禁用，所以不涉及 b 的工作
• 但实际出现总和 default 中 b 启用，prod 中 a 禁用，合并结果中 b 仍被启用

本 PR 调整了 Scanner & Loader 的插件配置部分逻辑：

• 将 pluginConfig 字段分拆到 refMap 和 extraPluginConfig（扫描时指定的）；
• load 阶段以 ref（插件/应用）为单位，每层按环境合并插件配置；
• 用上面按环境合并的配置排序、加载 itemList

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (a2e5f6d) 91.38% compared to head (5d50207) 91.34%.

Files	Patch %	Lines
src/configuration/index.ts	57.14%	3 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #272      +/-   ##
==========================================
- Coverage   91.38%   91.34%   -0.05%     
==========================================
  Files          49       49              
  Lines        1196     1202       +6     
  Branches      218      218              
==========================================
+ Hits         1093     1098       +5     
- Misses        103      104       +1     

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[JerrysShan]

标题修改下吧， fix