Bump MSRV to 1.70 #1321

Job	Run time
Rustfmt	16s
Test (1.70.0)	22s
Test (stable)	21s
Test (windows)	1m 3s
Test (macos)	18s
Test (beta)	24s
Test (nightly)	20s
Clippy	15s
check-external-types (ubuntu-latest)	14s
check-external-types (macos-latest)	17s
check-external-types (windows-latest)	31s
Check (aarch64-apple-darwin)	32s
Check (aarch64-apple-ios)	33s
Check (aarch64-apple-tvos)	35s
Check (aarch64-unknown-freebsd)	32s
Check (aarch64-unknown-linux-gnu)	34s
Check (aarch64-unknown-linux-ohos)	34s
Check (aarch64-apple-watchos)	34s
Check (aarch64-unknown-redox)	31s
Check (aarch64-unknown-netbsd)	34s
Check (armv7-linux-androideabi)	35s
Check (aarch64-unknown-openbsd)	32s
Check (aarch64-linux-android)	36s
Check (arm64_32-apple-watchos)	34s
Check (arm-linux-androideabi)	33s
Check (armv7-sony-vita-newlibeabihf)	33s
Check (aarch64-unknown-linux-musl)	36s
Check (i686-linux-android)	34s
Check (sparcv9-sun-solaris)	31s
Check (x86_64-apple-darwin)	34s
Check (i686-unknown-linux-gnu)	34s
Check (x86_64-unknown-dragonfly)	31s
Check (x86_64-pc-solaris)	33s
Check (x86_64-pc-cygwin)	33s
Check (x86_64-unknown-fuchsia)	36s
Check (x86_64-unknown-illumos)	32s
Check (armv7-unknown-linux-ohos)	34s
Check (x86_64-pc-windows-msvc)	33s
Check (x86_64-apple-ios)	33s
Check (x86_64-unknown-linux-ohos)	33s
Check (x86_64-unknown-netbsd)	36s
Check (x86_64-unknown-linux-musl)	33s
Check (x86_64-unknown-openbsd)	34s
Check (x86_64-unknown-linux-gnu)	33s
Check (x86_64-unknown-freebsd)	36s
Check (x86_64-unknown-redox)	33s
	23m 55s

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