feat(x86_64): real abstraction for ISA IRQs, unfuck I/O APIC #1401

Job	Run time
changed_paths	6s
clippy	2m 53s
rustfmt	14s
cargo test (cross x64)	4m 34s
Miri tests (cordyceps)	1m 57s
Loom tests (cordyceps)	1m 30s
docs	1m 54s
Tests (maitake, no-default-features)	1m 40s
cargo test (host)	4m 41s
build boot image (x86_64)	3m 16s
cargo check (host)	3m 28s
Loom tests (maitake)	4m 11s
Miri tests (maitake)	18m 42s
Loom tests (mycelium-util)	48s
all_systems_go	0s
	49m 54s

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