fix: type regression in vi.mocked() static class methods

[purepear]

Description

Fixes typeing regression in vitest@4+'s vi.mocked()

• Fixes vi.mocked(...) typing for static class methods by preserving mocked method members on shallow mocked constructors.
• Adds a regression test covering mockImplementation() on a static class method to prevent future type regressions.

Resolves #9172

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[hi-ogawa]

Makes sense. Thanks!