add support for logging parameters to MlflowLoggerHook

[eivtho]

Motivation

I want to log (hyper)parametrers in MLFLow to be able to compare them between runs.

Modification

Adds the argument "params" to MlflowLoggerHook. This works in the same way as the existing argument "tags" in that it runs mlflow.log_params() in before_run().

BC-breaking (Optional)

No.

Use cases (Optional)

See motivation.

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, like MMDet or MMCls.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.

[yaqi0510]

Dear eivtho,

First of all, we want to express our gratitude for your significant PR in the MMCV 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.

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Thank you again for your contribution❤

Best regards！@eivtho