stateless: Refactor pNext, flag and enum checking utils #10190

Job	Run time
code-format	28s
check_vvl	1m 4s
Ubuntu Backcompat	8m 32s
androidOnLinux	5m 15s
android (arm64-v8a, ON, c++_shared)	8m 14s
chromium (target_os="linux" target_cpu="x64")	8m 10s
android (armeabi-v7a, OFF, c++_static)	8m 52s
linux (address sanitizer, debug, robinhood ON )	30m 16s
chromium (target_os="android" target_cpu="arm64")	11m 0s
linux (address sanitizer, release, robinhood ON )	18m 30s
linux (thread sanitizer, release, robinhood ON )	8m 7s
linux (address sanitizer, release, robinhood OFF )	19m 17s
mingw	5m 10s
windows (amd64)	10m 28s
windows (amd64_x86)	10m 17s
iOS	3m 45s
androidUpload	0s
windowsUpload	0s
linux Upload	0s
	2h 37m 25s

Provide feedback