[Feature] Support file_client_args in LoadImageFromFile

[jin-s13]

Motivation

Support file_client_args in LoadImageFromFile. Similar to this in mmdet:

https://github.com/open-mmlab/mmdetection/blame/0b94be76b89fcbbfd83ef2a1a67818b5948280d1/mmdet/datasets/pipelines/loading.py#L12

Modification

LoadImageFromFile in loading.py

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

Attention: Patch coverage is 62.50000% with 6 lines in your changes missing coverage. Please review.

Please upload report for BASE (dev-0.22@4297d1e). Learn more about missing BASE report.

Files	Patch %	Lines
mmpose/datasets/pipelines/loading.py	62.50%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             dev-0.22    #1076   +/-   ##
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  Coverage            ?   83.35%           
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  Files               ?      196           
  Lines               ?    15156           
  Branches            ?     2739           
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  Hits                ?    12634           
  Misses              ?     1827           
  Partials            ?      695           

Flag	Coverage Δ
unittests	83.30% <62.50%> (?)

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