write: add `LineConvert` #527

Job	Run time
bench	1m 5s
Build fuzz targets	1m 23s
coverage	1m 2s
build (ubuntu-latest, stable)	41s
features	3m 8s
doc	29s
cross (i686-unknown-linux-gnu)	47s
build (ubuntu-latest, beta)	49s
cross (powerpc64-unknown-linux-gnu)	56s
build (ubuntu-latest, nightly)	41s
build (stable, macOS-latest)	41s
msrv	2m 30s
msrv-read	2m 35s
rustfmt	15s
Run `debug_abbrev` fuzz target	5m 6s
Run `debug_aranges` fuzz target	5m 6s
Run `debug_info` fuzz target	5m 7s
Run `debug_line` fuzz target	5m 5s
Run `eh_frame` fuzz target	5m 7s
Run `eh_frame_hdr` fuzz target	5m 5s
	47m 38s

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