Add a fallible Rect::try_inner_rect method that never panics #55

Job	Run time
Linux (1.56.0)	4m 22s
Linux (stable)	33s
Linux (beta)	28s
Linux (nightly)	29s
Linux (--features serde, 1.56.0)	4m 30s
Linux (--features serde, stable)	30s
Linux (--features serde, beta)	36s
Linux (--features serde, nightly)	35s
Linux (--no-default-features --features libm, 1.56.0)	5m 9s
Linux (--no-default-features --features libm, stable)	39s
Linux (--no-default-features --features libm, beta)	34s
Linux (--no-default-features --features libm, nightly)	30s
Linux (stable, --features mint)	32s
Linux (stable, --features bytemuck)	37s
Linux (stable, --features arbitrary)	33s
Linux (nightly, --features unstable)	31s
Linux (nightly, --features unstable,serde)	40s
Result	2s
	21m 50s

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