Implement lossless From methods for Duration conversions #609

Job	Run time
Coverage	40s
Lints	19s
Check	17s
Test Suite (ubuntu-latest, MSRV)	2m 48s
no-std build (aarch64-unknown-none)	24s
Test Suite (ubuntu-latest, stable)	2m 39s
no-std build (thumbv6m-none-eabi)	20s
Test Suite (macos-latest, MSRV)	1m 48s
Test Suite (macos-latest, stable)	1m 47s
Test Suite (windows-latest, MSRV)	8m 39s
Test Suite (windows-latest, stable)	8m 57s
Release	0s
	28m 38s

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