Backport #30240 by wxiaoguang
Major changes:
* Move some functions like "addReader" / "isSubDir" /
"addRecursiveExclude" to a separate package, and add tests
* Clarify the filename&dump type logic and add tests
* Clarify the logger behavior and remove FIXME comments
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
