chore(general): bump MSRV to 1.81, use `core::error::Error` on `no-st… #5224

Job	Run time
doctest	3m 29s
feature-checks	8m 56s
test ubuntu-latest stable --no-default-features	2m 57s
test ubuntu-latest stable	3m 1s
wasm-unknown	2m 56s
test ubuntu-latest stable --all-features	3m 35s
wasm-wasi	4m 11s
test ubuntu-latest nightly --no-default-features	1m 23s
test ubuntu-latest nightly	1m 24s
check no_std	1m 3s
clippy	2m 0s
test ubuntu-latest nightly --all-features	2m 15s
test ubuntu-latest 1.81 --no-default-features	1m 58s
test ubuntu-latest 1.81	1m 54s
docs	1m 3s
fmt	12s
test windows-latest stable --no-default-features	6m 30s
test windows-latest stable	5m 46s
test windows-latest stable --all-features	7m 0s
test windows-latest nightly --no-default-features	4m 0s
test windows-latest nightly	4m 50s
test windows-latest nightly --all-features	4m 47s
test windows-latest 1.81 --no-default-features	4m 45s
test windows-latest 1.81	4m 8s
ci success	8s
	1h 24m 11s

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