Implement cat related operations in the AysncOSSFileSystem

[karajan1001]

fix: #96

1. Add cat_file to the AioOSSFileSystem
2. Add modified to the AioOSSFileSystem
3. Make tests passed related to cat and modified

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.10 :tada:

Comparison is base (adbff11) 92.50% compared to head (e5e4e42) 92.61%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #113 +/- ## ========================================== + Coverage 92.50% 92.61% +0.10% ========================================== Files 13 13 Lines 1694 1719 +25 Branches 344 349 +5 ========================================== + Hits 1567 1592 +25 Misses 85 85 Partials 42 42 ``` | [Impacted Files](https://codecov.io/gh/fsspec/ossfs/pull/113?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [src/ossfs/async\_oss.py](https://codecov.io/gh/fsspec/ossfs/pull/113?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29zc2ZzL2FzeW5jX29zcy5weQ==) | `83.94% <100.00%> (+0.96%)` | :arrow_up: | | [src/ossfs/core.py](https://codecov.io/gh/fsspec/ossfs/pull/113?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-c3JjL29zc2ZzL2NvcmUucHk=) | `83.14% <100.00%> (+0.26%)` | :arrow_up: | | [tests/test\_file.py](https://codecov.io/gh/fsspec/ossfs/pull/113?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dGVzdHMvdGVzdF9maWxlLnB5) | `100.00% <100.00%> (ø)` | | | [tests/test\_object.py](https://codecov.io/gh/fsspec/ossfs/pull/113?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dGVzdHMvdGVzdF9vYmplY3QucHk=) | `99.50% <100.00%> (+<0.01%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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