platform: simplify setting CORE_COUNT and MAX_CORE_COUNT #21662

Job	Run time
LP64-WIP	4m 21s
build-windows (imx8 imx8x imx8m imx8ulp)	13m 40s
build-windows (mtl lnl)	12m 7s
build-windows (-d, lnl)	8m 51s
manifest-check	3m 10s
build-windows (ptl)	10m 0s
build-linux (mnfst, imx8 imx8x imx8m imx8ulp)	7m 0s
build-linux (mnfst, tgl tgl-h)	5m 57s
build-linux (zmain, imx8 imx8x imx8m imx8ulp)	6m 44s
build-linux (zmain, tgl tgl-h)	6m 1s
build-linux (zmain, ptl)	4m 29s
build-linux (mnfst, --all)	17m 10s
build-linux (zmain, mtl lnl)	5m 49s
build-linux (mnfst, ptl)	4m 51s
build-linux (mnfst, mtl lnl)	5m 54s
build-linux (-d, mnfst, lnl)	4m 43s
build-windows (tgl tgl-h)	12m 15s
compare-linux-win	2m 34s
	2h 15m 36s

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