fix: should call config hook in idle callback

[whxaxes]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

config 的 lifecycle hook 是 loader 事件触发，当不存在 config 文件的时候不会触发 loader 的 before/after 事件，导致 config 的 lifecycle hook 也不会触发

所以在 loader 事件中加个 idle 事件，用于当某个 loader 没有被触发时回调，从而解决 config loader 没有使用时也能触发 configWillLoad 及 configDidLoad

根据 DEFAULT_LOADER_LIST_WITH_ORDER 进行分组，分组后按顺序执行，保证内置的每个 loader 的 before/after 都会触发

[codecov-commenter]

Codecov Report

Base: 92.42% // Head: 92.42% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (894aeb8) compared to base (9f3b77c).
Patch coverage: 93.33% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #218   +/-   ##
=======================================
  Coverage   92.42%   92.42%           
=======================================
  Files          55       55           
  Lines        1293     1294    +1     
  Branches      218      216    -2     
=======================================
+ Hits         1195     1196    +1     
  Misses         98       98           

Impacted Files	Coverage Δ
src/loader/factory.ts	92.78% <93.33%> (+0.07%)	⬆️

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[whxaxes]

CI 挂了，我看一下

[hyj1991]

SGTM

[noahziheng]

LGTM