x86_64: make GDT core-local after boot and load TSS #112

Job	Run time
lint-clippy	1m 28s
lint-rustfmt	38s
boot-protocol-header	44s
build-kernel-aarch64 (dev, --all-features)	52s
build-limine-aarch64 (dev, --all-features)	48s
build-limine-x86_64 (dev, --all-features)	1m 1s
build-kernel-aarch64 (dev, --no-default-features)	48s
build-limine-aarch64 (dev, --no-default-features)	49s
lint-docs	1m 30s
build-limine-x86_64 (dev, --no-default-features)	1m 8s
build-kernel-aarch64 (release, --all-features)	59s
build-limine-aarch64 (release, --all-features)	48s
build-limine-x86_64 (release, --all-features)	54s
build-kernel-aarch64 (release, --no-default-features)	49s
build-limine-x86_64 (release, --no-default-features)	57s
build-limine-aarch64 (release, --no-default-features)	44s
unit-test	54s
build-kernel-x86_64 (dev, --all-features)	1m 6s
lint-python	12s
build-kernel-x86_64 (dev, --no-default-features)	56s
build-kernel-x86_64 (release, --all-features)	1m 2s
build-kernel-x86_64 (release, --no-default-features)	56s
	20m 3s

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