Report proposal errors earlier and more precisely where possible #5578

Job	Run time
Bitrot check	1m 46s
Latest build on ubuntu-latest	2m 5s
Check ZFuture build on Linux	24s
Latest build on windows-latest	3m 49s
Check ZFuture build on macOS	31s
Clippy (MSRV)	1m 28s
Check ZFuture build on Windows	4m 11s
Clippy (beta)	11s
Code coverage	18m 34s
Latest build on macOS-latest	1m 47s
Intra-doc links	1m 56s
Rustfmt	13s
protobuf consistency	1m 10s
Test on Linux	9m 7s
UUID validity	3s
Test Orchard on Linux	10m 40s
Test NU6 on Linux	9m 1s
Test on macOS	10m 19s
Build target wasm32-wasi	56s
Test Orchard on macOS	10m 57s
Test on Windows	15m 43s
Test Orchard on Windows	18m 30s
Test NU6 on Windows	15m 8s
	2h 18m 29s

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