fix(runtime-core): should not take unmount children fast path if children contain cached nodes

[edison1105]

close #5154

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	85.9 kB (+53 B)	32.7 kB (+12 B)	29.5 kB (+14 B)
vue.global.prod.js	132 kB (+96 B)	49.4 kB (+26 B)	44.4 kB (+19 B)

Usages

Name	Size	Gzip	Brotli
createApp	47.9 kB (+52 B)	18.9 kB (+23 B)	17.2 kB (+13 B)
createSSRApp	50.7 kB (+52 B)	20 kB (+24 B)	18.2 kB (+21 B)
defineCustomElement	50.3 kB (+52 B)	19.7 kB (+17 B)	17.9 kB (+18 B)
overall	61.3 kB (+52 B)	23.7 kB (+21 B)	21.6 kB (+8 B)

[yyx990803]

The direction is right, but checking only the direct children of the current vnode does not account for deeply nested v-once cached nodes.

In d343a0d I use setBlockTracking to mark the entire block to avoid this problem.