elastic scaling: rework core selector handling #16812

Job	Run time
check-dependency-rules	9s
check-fail-ci	10s
check-markdown	21s
check-readme	3m 29s
check-workspace	18s
preflight / preflight	47s
preflight / ci-versions	56s
fmt	1m 4s
check-rust-feature-propagation	1m 55s
check-toml-format	1m 1s
check-umbrella	2m 12s
test-rust-features	1m 54s
All quick checks passed	1s
	14m 17s

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