Remove thiserror and smallvec deps #2286

Job	Run time
Lint	14s
Docs	19s
Test	42s
build_versions (stable)	19s
Test (charset)	37s
Test	23s
build_versions (beta)	20s
Test (cookies)	46s
Test (charset)	26s
build_versions (1.67.0)	24s
Test (socks-proxy)	38s
Test (cookies)	28s
Test (gzip)	35s
Test (socks-proxy)	33s
Test (brotli)	33s
cargo-deny (aarch64-apple-ios)	21s
Test (gzip)	35s
Test (json)	46s
cargo-deny (aarch64-linux-android)	17s
Test (brotli)	38s
Test (native-tls)	49s
cargo-deny (i686-pc-windows-gnu)	16s
Test (json)	27s
cargo-deny (i686-pc-windows-msvc)	21s
Test (native-tls)	40s
cargo-deny (i686-unknown-linux-gnu)	20s
cargo-deny (wasm32-unknown-unknown)	17s
cargo-deny (x86_64-apple-darwin)	21s
cargo-deny (x86_64-apple-ios)	19s
cargo-deny (x86_64-pc-windows-gnu)	23s
cargo-deny (x86_64-pc-windows-msvc)	17s
cargo-deny (x86_64-unknown-linux-gnu)	19s
cargo-deny (x86_64-unknown-redox)	22s
	15m 5s

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