schedule: zephyr_ll_user: improve heap init and make it usable from user-space #23212

Job	Run time
manifest-check	2m 39s
build-linux (mnfst, imx8m imx8ulp)	4m 48s
LP64-WIP	4m 2s
build-linux (mnfst, tgl)	4m 8s
build-linux (mnfst, ptl)	4m 51s
build-linux (mnfst, tgl-h)	4m 30s
build-linux (-d, mnfst, lnl)	5m 10s
build-linux (mnfst, wcl imx95)	7m 38s
build-linux (mnfst, lnl)	4m 19s
build-windows (mnfst, imx8 imx8x)	11m 51s
build-linux (mnfst, imx8 imx8x)	5m 31s
build-windows (mnfst, imx8m imx8ulp)	9m 3s
build-windows (mnfst, mtl)	9m 41s
build-windows (-d, mnfst, lnl)	8m 48s
build-windows (mnfst, tgl)	9m 23s
build-windows (mnfst, lnl)	9m 59s
build-linux (mnfst, mtl)	4m 35s
build-windows (mnfst, ptl)	10m 6s
build-windows (mnfst, tgl-h)	9m 40s
compare-linux-win	29s
	2h 11m 11s

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