refactor: Remove slot mutex and simplify per blob state #494

Job	Run time
Cross Build Only (x86_64-unknown-freebsd)	51s
Android Build Only (armv7-linux-androideabi)	1m 9s
Android Build Only (aarch64-linux-android)	1m 10s
Cross Test (i686-unknown-linux-gnu)	1m 44s
Checking fmt	47s
Checking docs	52s
cargo deny	27s
clippy_check	1m 30s
check_semver	1m 18s
codespell	8s
Minimal Supported Rust Version	1m 0s
CI Test Suite / Tests (windows-latest, stable, default, x86_64-pc-windows-msvc)	2m 1s
CI Test Suite / Tests (macOS-arm-latest, stable, all)	1m 42s
CI Test Suite / Tests (windows-latest, stable, none, x86_64-pc-windows-msvc)	2m 2s
CI Test Suite / Tests (windows-latest, stable, all, x86_64-pc-windows-msvc)	2m 0s
CI Test Suite / Tests (ubuntu-latest, stable, none)	1m 32s
CI Test Suite / Tests (ubuntu-latest, stable, all)	1m 39s
CI Test Suite / Tests (ubuntu-latest, stable, default)	1m 32s
CI Test Suite / Tests (macOS-arm-latest, stable, none)	1m 40s
CI Test Suite / Tests (macOS-arm-latest, stable, default)	1m 40s
	26m 44s

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