Fix Python 3.7 compatibility in legacy test workflow

[Copilot]

Two steps in the Python 3.7 legacy test workflow had identical names "Run tests", making CI failure diagnosis ambiguous. Additionally, the tests were failing due to Python 3.7 lacking AsyncMock and IsolatedAsyncioTestCase in its standard library.

Changes:

• Renamed dependency installation step from "Run tests" to "Install dependencies"
• Actual test execution step retains "Run tests" name
• Added fallback import for AsyncMock in tests/utils/_mock.py to support Python 3.7 (uses asyncmock package when unittest.mock.AsyncMock is not available)
• Added compatibility shim for IsolatedAsyncioTestCase in tests/test_async_vinted_wrapper.py for Python 3.7 (this class was introduced in Python 3.8)

This ensures CI logs clearly distinguish between dependency installation failures and test execution failures, and enables the test suite to run successfully on Python 3.7.

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[Giglium]

@copilot the python legacy test is still failing

[Copilot]

@copilot the python legacy test is still failing

Fixed the Python 3.7 compatibility issue. The test was failing because AsyncMock doesn't exist in Python 3.7's standard library. Added a fallback import to use the asyncmock package for Python 3.7. (commit ab88a38)

[Giglium]

@copilot nice! Now the error is: AttributeError: module 'unittest' has no attribute 'IsolatedAsyncioTestCase' Can you also solve this one?

[Copilot]

@copilot nice! Now the error is: AttributeError: module 'unittest' has no attribute 'IsolatedAsyncioTestCase' Can you also solve this one?

Fixed the IsolatedAsyncioTestCase compatibility issue. Python 3.7 doesn't have this class (introduced in Python 3.8), so I added a compatibility shim that provides the same functionality for Python 3.7. (commit ef79b98)