[Refactor] Refactor SimpleBaseline3d and VideoPose3d

[LareinaM]

Motivation

Modification

BC-breaking (Optional)

Use cases (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Patch coverage: 48.88% and project coverage change: -2.72 ⚠️

Comparison is base (b647b8c) 82.01% compared to head (e80a82b) 79.29%.

❗ Current head e80a82b differs from pull request most recent head 56b0c1a. Consider uploading reports for the commit 56b0c1a to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2420      +/-   ##
===========================================
- Coverage    82.01%   79.29%   -2.72%     
===========================================
  Files          233      248      +15     
  Lines        13653    14859    +1206     
  Branches      2322     2577     +255     
===========================================
+ Hits         11197    11782     +585     
- Misses        1916     2499     +583     
- Partials       540      578      +38     

Flag	Coverage Δ
unittests	79.29% <48.88%> (-2.72%)	⬇️

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

Impacted Files	Coverage Δ
mmpose/codecs/regression_label.py	87.09% <ø> (ø)
mmpose/models/heads/__init__.py	100.00% <ø> (ø)
mmpose/models/pose_estimators/base.py	81.08% <0.00%> (-2.26%)	⬇️
mmpose/apis/inference_3d.py	7.56% <7.56%> (ø)
mmpose/apis/inference.py	68.96% <7.69%> (-7.74%)	⬇️
mmpose/visualization/local_visualizer_3d.py	8.33% <8.33%> (ø)
mmpose/apis/inference_tracking.py	11.53% <11.53%> (ø)
mmpose/datasets/transforms/formatting.py	66.27% <15.00%> (-16.08%)	⬇️
mmpose/models/pose_estimators/pose_lifter.py	17.11% <17.11%> (ø)
...heads/regression_heads/temporal_regression_head.py	36.00% <36.00%> (ø)
... and 24 more

... and 1 file 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.

[Tau-J]

Could you please fix the lint?

[Tau-J]

LGTM