deps(python): drop Python 3.7 support

[XuehaiPan]

Description

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Motivation and Context

Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.
You can use the syntax close #15213 if this solves the issue #15213

• I have raised an issue to propose this change (required for new features and bug fixes)

Python 3.7 is reaching its end-of-life schedule on 27 Jun 2023. Although there still have 4 months to have support. There are many of our dependencies, such as PyTorch and lint tools, are dropping Python 3.7 support.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)
• Example (update in the folder of example)

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.
• I have reformatted the code using make format. (required)
• I have checked the code using make lint. (required)
• I have ensured make test pass. (required)

[codecov]

Codecov Report

Base: 91.89% // Head: 91.97% // Increases project coverage by +0.08% 🎉

Coverage data is based on head (6f97f7c) compared to base (14962cf).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #136      +/-   ##
==========================================
+ Coverage   91.89%   91.97%   +0.08%     
==========================================
  Files          66       66              
  Lines        2539     2564      +25     
==========================================
+ Hits         2333     2358      +25     
  Misses        206      206              

Flag	Coverage Δ
unittests	91.97% <100.00%> (+0.08%)	⬆️

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

Impacted Files	Coverage Δ
torchopt/base.py	86.36% <100.00%> (+0.21%)	⬆️
torchopt/diff/zero_order/decorator.py	96.94% <100.00%> (+0.11%)	⬆️
torchopt/typing.py	100.00% <100.00%> (ø)
torchopt/utils.py	86.77% <100.00%> (-0.07%)	⬇️
torchopt/accelerated_op/adam_op.py	100.00% <0.00%> (ø)
torchopt/diff/implicit/decorator.py	95.73% <0.00%> (+0.06%)	⬆️
torchopt/diff/implicit/nn/module.py	82.14% <0.00%> (+0.66%)	⬆️
torchopt/diff/zero_order/nn/module.py	91.67% <0.00%> (+0.76%)	⬆️

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[Benjamin-eecs]

source: pytorch/pytorch#93155