feat(x86_64): real abstraction for ISA IRQs, unfuck I/O APIC #1402

Job	Run time
changed_paths	7s
cargo check (host)	3m 27s
rustfmt	14s
Loom tests (cordyceps)	1m 25s
clippy	2m 46s
docs	1m 54s
cargo test (cross x64)	4m 44s
cargo test (host)	4m 45s
build boot image (x86_64)	3m 7s
Miri tests (cordyceps)	2m 6s
Loom tests (maitake)	4m 11s
Miri tests (maitake)	18m 39s
Tests (maitake, no-default-features)	1m 46s
Loom tests (mycelium-util)	51s
all_systems_go	0s
	50m 2s

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