config: suggest the correct form when key contains "=" in set context #27989

Job	Run time
config	7s
fuzz smoke test	1m 11s
win build	3m 54s
sparse	3m 45s
win+VS build	-1s
static-analysis	5m 39s
rust-analysis	1m 28s
osx-gcc (macos-14)	16m 50s
win+Meson build	4m 31s
documentation	7m 1s
osx-reftable (macos-14)	21m 43s
osx-clang (macos-14)	20m 44s
osx-meson (macos-14)	6h 0m 16s
linux-musl-meson (alpine:latest)	7m 48s
linux-meson (ubuntu:rolling)	11m 44s
debian-11 (debian:11)	10m 34s
linux-leaks (ubuntu:rolling)	29m 2s
linux-breaking-changes (ubuntu:rolling)	12m 23s
linux-reftable (ubuntu:rolling)	1m 21s
linux32 (i386/ubuntu:focal)	10m 14s
linux-sha256 (ubuntu:rolling)	1m 18s
almalinux-8 (almalinux:8)	10m 27s
linux-reftable-leaks (ubuntu:rolling)	30m 29s
linux-TEST-vars (ubuntu:20.04)	8m 52s
linux-asan-ubsan (ubuntu:rolling)	1m 19s
fedora-breaking-changes-meson (fedora:latest)	9m 50s
win+VS test	0s
win test (6)	9m 7s
win test (2)	8m 16s
win test (5)	6m 17s
win test (0)	7m 18s
win test (9)	10m 22s
win test (3)	8m 52s
win test (4)	8m 39s
win test (7)	6m 10s
win test (8)	5m 51s
win test (1)	7m 46s
win+Meson test (5)	9m 22s
win+Meson test (3)	6m 17s
win+Meson test (7)	7m 56s
win+Meson test (1)	10m 24s
win+Meson test (6)	9m 26s
win+Meson test (2)	9m 52s
win+Meson test (8)	8m 14s
win+Meson test (4)	5m 29s
win+Meson test (9)	8m 19s
win+Meson test (0)	7m 47s
	12h 34m 13s

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