adopt core::error::Error, update nightly, update bootloader #1427

Job	Run time
changed_paths	5s
rustfmt	12s
cargo test (host)	4m 37s
cargo check (host)	3m 36s
build boot image (x86_64)	3m 38s
clippy	2m 39s
Loom tests (cordyceps)	1m 24s
docs	4m 8s
cargo test (cross x64)	4m 50s
Miri tests (cordyceps)	2m 56s
Loom tests (maitake)	4m 10s
Miri tests (maitake)	33m 24s
Tests (maitake, no-default-features)	1m 30s
all_systems_go	0s
	1h 7m 9s

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