Update to the new backtrace API #303

Job	Run time
Clippy (stable)	28s
Check (stable)	20s
Miri	1m 11s
Rustfmt (stable)	14s
Test Suite	4m 14s
Test Suite (stable)	46s
Test Suite (--no-default-features)	4m 13s
Test Suite (ubuntu-latest)	41s
Test Suite (--features track-caller)	4m 17s
Test Suite (stable, --no-default-features)	47s
Test Suite (windows-latest)	1m 32s
Test Suite (--features auto-install)	4m 22s
Test Suite (stable, --features track-caller)	47s
Test Suite (macOS-latest)	1m 11s
Test Suite (stable, --features pyo3)	44s
Test Suite (stable, --features auto-install)	46s
Test Suite (stable, --all-features)	46s
Test Suite (beta)	41s
Test Suite (beta, --no-default-features)	40s
Test Suite (beta, --features track-caller)	42s
Test Suite (beta, --features pyo3)	43s
Test Suite (beta, --features auto-install)	40s
Test Suite (beta, --all-features)	43s
Test Suite (nightly)	42s
Test Suite (nightly, --no-default-features)	41s
Test Suite (nightly, --features track-caller)	42s
Test Suite (nightly, --features pyo3)	46s
Test Suite (nightly, --features auto-install)	45s
Test Suite (nightly, --all-features)	44s
	35m 48s

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