Fix typos and remove fullwidth unicode chars

[evdcush]

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Motivation

There are "fullwidth" unicode characters (mostly punctuation symbols) used in various places in MMEngine's documentation. These characters should not be used in EN documentation, as they are not generally supported by various documentation builds, such as latexpdf, and can cause issues with static analysis tools.

There are also various fixes to typos included in this branch, including some to paths in source code.

Related to #1018

Modification

• Replace fullwidth unicode chars with ascii equivalents
• Fix typos
  • Fix module name and import these have been reverted to avoid BC

BC-breaking (Optional)

N/A

Use cases (Optional)

N/A

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDetection or MMPretrain.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[evdcush]

These test failures appear unrelated to my diffs 👇🏻

[evdcush]

@Harold-lkk @HAOCHENYE @C1rN09 @zhouzaida

May I receive a review please?

[zhouzaida]

Hi @evdcush , thanks for your contribution. Last week we were on vacation and I am reviewing this PR now.

[evdcush]

Hi @zhouzaida, thank you for your review! 🙇🏻‍♂️

I have undone the diffs you mentioned as potential BC.