[Refactor] Change the directory hierarchy

[KKIEEK]

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Motivation

Please describe the motivation of this PR and the goal you want to achieve through this PR.

Modification

Please briefly describe what modification is made in this PR.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@58bf811). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head 8441977 differs from pull request most recent head d61bb5b. Consider uploading reports for the commit d61bb5b to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #110   +/-   ##
=======================================
  Coverage        ?   72.79%           
=======================================
  Files           ?       59           
  Lines           ?     1632           
  Branches        ?      235           
=======================================
  Hits            ?     1188           
  Misses          ?      345           
  Partials        ?       99           

Flag	Coverage Δ
unittests	72.79% <0.00%> (?)

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[yhna940]

LGTM