fix(parser): add `no_std` support for `CustomError` #1941

Job	Run time
miri --no-default-features	4m 9s
miri	4m 10s
test ubuntu-latest stable --no-default-features	28s
miri --all-features	5m 18s
test ubuntu-latest stable	30s
test ubuntu-latest beta --no-default-features	1m 30s
clippy	25s
test ubuntu-latest beta	1m 29s
docs	54s
test ubuntu-latest nightly --no-default-features	1m 14s
feature-checks	35s
test ubuntu-latest nightly	1m 18s
fmt	14s
test ubuntu-latest 1.65 --no-default-features	2m 18s
test ubuntu-latest 1.65	2m 27s
wasm	20s
test windows-latest stable --no-default-features	1m 39s
test windows-latest stable	1m 11s
test windows-latest beta --no-default-features	2m 56s
test windows-latest beta	3m 25s
test windows-latest nightly --no-default-features	2m 54s
test windows-latest nightly	3m 16s
test windows-latest 1.65 --no-default-features	3m 15s
test windows-latest 1.65	3m 6s
test ubuntu-latest 1.65 --features json	2m 27s
test windows-latest 1.65 --features json	3m 22s
test ubuntu-latest stable --all-features	30s
test ubuntu-latest beta --all-features	1m 39s
test ubuntu-latest nightly --all-features	1m 26s
	58m 25s

Provide feedback