refactor: Remove slot mutex and simplify per blob state #484

Job	Run time
Android Build Only (aarch64-linux-android)	1m 26s
Android Build Only (armv7-linux-androideabi)	1m 8s
Cross Test (i686-unknown-linux-gnu)	1m 45s
Checking fmt	16s
Cross Build Only (x86_64-unknown-freebsd)	49s
check_semver	1m 6s
Checking docs	1m 8s
Minimal Supported Rust Version	1m 3s
clippy_check	1m 35s
cargo deny	28s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	2m 4s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 5s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 7s
CI Test Suite / Tests (ubuntu-latest, stable, none)	1m 19s
codespell	6s
CI Test Suite / Tests (ubuntu-latest, stable, all)	1m 30s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	1m 36s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	1m 44s
CI Test Suite / Tests (ubuntu-latest, stable, default)	1m 29s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	1m 36s
	26m 20s

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