feat(x86_64): real abstraction for ISA IRQs, unfuck I/O APIC #1407

Job	Run time
changed_paths	4s
cargo test (host)	4m 56s
cargo check (host)	3m 37s
clippy	2m 47s
build boot image (x86_64)	3m 8s
Loom tests (cordyceps)	1m 34s
docs	4m 23s
rustfmt	12s
cargo test (cross x64)	4m 27s
Miri tests (cordyceps)	2m 1s
Loom tests (maitake)	4m 10s
Miri tests (maitake)	17m 57s
Tests (maitake, no-default-features)	1m 45s
all_systems_go	1s
	51m 2s

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