Raise TypeError for invalid cert values

[Abdulmumin1]

Fixes #844.

Summary

• normalize supported cert shapes before calling SSLContext.load_cert_chain
• raise TypeError for unsupported cert values instead of silently ignoring them
• add regression coverage for pathlib.Path, empty tuple, and invalid tuple lengths

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

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_{Comparing Abdulmumin1:fix-cert-type-error (f4f8064) with main (999da32)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩