[Feature] Add argument 'repeat' to SRREDSMultipleGTDataset

[ckkelvinchan]

Motivation

As indicated in #671, training BasicVSR++ with 8 GPUs causes an error, since REDS4 contains 4 validation folders, which cannot be tested with 8 GPUs. This PR fixes the issue by repeating the validation data (e.g. from 4 folders to 8)

Modification

1. Modify mmedit/datasets/sr_reds_multiple_gt_dataset.py
2. Modify config of BasicVSR++

[codecov]

Codecov Report

Merging #672 (af7b8d5) into master (9e7d78f) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #672      +/-   ##
==========================================
- Coverage   80.67%   80.65%   -0.02%     
==========================================
  Files         199      199              
  Lines       11371    11375       +4     
  Branches     1818     1819       +1     
==========================================
+ Hits         9173     9175       +2     
- Misses       1915     1916       +1     
- Partials      283      284       +1     

Flag	Coverage Δ
unittests	80.64% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
mmedit/datasets/sr_reds_multiple_gt_dataset.py	100.00% <100.00%> (ø)
...ls/components/stylegan2/generator_discriminator.py	84.93% <0.00%> (-1.21%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9e7d78f...af7b8d5. Read the comment docs.