[Feature] Add BioMedicalRandomGamma

[Fivethousand5k]

Add the random gamma correction transform for biomedical images, which follows the design of the nnUNet.

[codecov]

Codecov Report

Base: 83.52% // Head: 83.43% // Decreases project coverage by -0.08% ⚠️

Coverage data is based on head (a12e5a6) compared to base (26f3df7).
Patch coverage: 55.55% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2406      +/-   ##
===========================================
- Coverage    83.52%   83.43%   -0.09%     
===========================================
  Files          144      144              
  Lines         8302     8356      +54     
  Branches      1237     1246       +9     
===========================================
+ Hits          6934     6972      +38     
- Misses        1172     1178       +6     
- Partials       196      206      +10     

Flag	Coverage Δ
unittests	83.43% <55.55%> (-0.09%)	⬇️

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

Impacted Files	Coverage Δ
mmseg/datasets/__init__.py	100.00% <ø> (ø)
mmseg/datasets/transforms/__init__.py	100.00% <ø> (ø)
mmseg/datasets/transforms/transforms.py	91.29% <55.55%> (-1.92%)	⬇️

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[openmmlab-bot]

Fivethousand5k ，您好！您在MMSeg项目中给我们提的PR非常重要，感谢您付出私人时间帮助改进开源项目，相信很多开发者会从你的PR中受益。
我们非常期待与您继续合作，OpenMMLab专门成立了贡献者组织MMSIG，为贡献者们提供开源证书、荣誉体系和专享好礼，可通过添加微信：openmmlabwx 联系我们（请备注mmsig+GitHub id），由衷希望您能加入！
Dear Fivethousand5k,
First of all, we want to express our gratitude for your significant PR in the MMSeg project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
We are looking forward to continuing our collaboration with you. OpenMMLab has established a special contributors' organization called MMSIG, which provides contributors with open-source certificates, a recognition system, and exclusive rewards. You can contact us by adding our WeChat（if you have WeChat): openmmlab_wx, or join in our discord： https://discord.gg/qH9fysxPDW. We sincerely hope you will join us!
Best regards！ @Fivethousand5k