[Feature] Support dinov2 backbone

[fangyixiao18]

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

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.

BC-breaking (Optional)

Does the modification introduce changes that break the backward compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here and update the documentation.

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects, like MMDet or MMSeg.
• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.84 🎉

Comparison is base (c9a0cb0) 84.37% compared to head (227048c) 85.21%.

❗ Current head 227048c differs from pull request most recent head 0a0ac8a. Consider uploading reports for the commit 0a0ac8a to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1522      +/-   ##
==========================================
+ Coverage   84.37%   85.21%   +0.84%     
==========================================
  Files         142      239      +97     
  Lines        9925    17949    +8024     
  Branches     1621     2802    +1181     
==========================================
+ Hits         8374    15296    +6922     
- Misses       1277     2133     +856     
- Partials      274      520     +246     

Flag	Coverage Δ
unittests	85.21% <ø> (+0.84%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 381 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[Ezra-Yu]

LGTM.