[move] Remove move-explain and errmapgen #69704

Job	Run time
diff	7s
license-check	1m 8s
test (ubuntu-ghcloud)	23m 24s
test-extra (ubuntu-ghcloud)	13m 24s
release-notes-check	13s
move-auto-formatter-ci-test	0s
simtest	14m 43s
windows-build (windows-ghcloud)	18m 34s
cargo-deny (advisories, licenses, bans, ...)	2m 12s
clippy	7m 19s
graphql-rpc	22m 5s
move-test	0s
rustfmt	16s
cutting a new execution layer	1m 29s
test-extra	0s
test	0s
	1h 44m 54s

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