Migrate pallet-examples-split to use umbrella crate #19233

Job	Run time
check-dependency-rules	9s
check-fail-ci	31s
check-readme	4m 38s
check-markdown	27s
check-workspace	31s
preflight / preflight	1m 27s
preflight / ci-versions	1m 14s
check-toml-format	1m 21s
fmt	1m 26s
check-rust-feature-propagation	2m 16s
check-umbrella	2m 20s
test-rust-features	2m 1s
All quick checks passed	1s
	18m 22s

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