feat(x86_64): real abstraction for ISA IRQs, unfuck I/O APIC #1404

Job	Run time
changed_paths	8s
cargo test (host)	4m 44s
cargo check (host)	3m 49s
clippy	2m 55s
Loom tests (cordyceps)	1m 46s
build boot image (x86_64)	3m 16s
docs	2m 4s
rustfmt	25s
cargo test (cross x64)	5m 15s
Miri tests (cordyceps)	2m 13s
Loom tests (maitake)	4m 18s
Miri tests (maitake)	18m 19s
Tests (maitake, no-default-features)	1m 56s
Loom tests (mycelium-util)	1m 4s
all_systems_go	0s
	52m 12s

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