[Feature] Add scheduler visualization from mmpretrain to mmocr

[A-new-b]

Motivation

Transfer the scheduler visualization tool from mmpretrain to mmocr.

Modification

1. create /tools/visualizations/vis_scheduler.py.
2. move /tools/analysis_tools/browse_dataset.py to /tools/visualizations/browse_dataset.py.
3. modify /docs/zh_cn/user_guides/useful_tools.md and /docs/en/user_guides/useful_tools.md for scheduler visualization tool.

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 test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

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

[gaotongxiao]

And the linting test seems not passed.

You can install pre-commit hooks to automatically fix this issue:

pip install -U pre-commit
pre-commit install
pre-commit run --all-files
git add --update
git commit

[A-new-b]

And the linting test seems not passed.

You can install pre-commit hooks to automatically fix this issue:

pip install -U pre-commit
pre-commit install
pre-commit run --all-files
git add --update
git commit

I have fixed it

[gaotongxiao]

LGTM