feat: Define monoio MSRV to 1.80 #646

Job	Run time
test (x86_64-unknown-linux-gnu, stable)	7m 20s
test (x86_64-unknown-linux-gnu, nightly)	7m 14s
test (i686-unknown-linux-gnu, stable)	1m 32s
test (i686-unknown-linux-gnu, nightly)	1m 38s
test (aarch64-unknown-linux-gnu, stable)	1m 33s
test (aarch64-unknown-linux-gnu, nightly)	1m 37s
test (armv7-unknown-linux-gnueabihf, stable)	1m 33s
test (armv7-unknown-linux-gnueabihf, nightly)	1m 28s
test (riscv64gc-unknown-linux-gnu, stable)	1m 32s
test (riscv64gc-unknown-linux-gnu, nightly)	1m 30s
test (s390x-unknown-linux-gnu, stable)	1m 33s
test (s390x-unknown-linux-gnu, nightly)	1m 36s
test (x86_64-apple-darwin, stable)	4m 2s
test (x86_64-apple-darwin, nightly)	4m 7s
test (aarch64-apple-darwin, stable)	2m 53s
test (aarch64-apple-darwin, nightly)	3m 18s
test (x86_64-pc-windows-gnu, stable)	5m 12s
test (x86_64-pc-windows-gnu, nightly)	4m 29s
test (x86_64-pc-windows-msvc, stable)	4m 40s
test (x86_64-pc-windows-msvc, nightly)	5m 33s
test (i686-pc-windows-gnu, stable)	7m 57s
test (i686-pc-windows-gnu, nightly)	9m 6s
test (i686-pc-windows-msvc, stable)	6m 17s
test (i686-pc-windows-msvc, nightly)	4m 57s
	1h 32m 37s

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