stateless: Refactor pNext, flag and enum checking utils #10187

Job	Run time
code-format	32s
check_vvl	1m 3s
linux (address sanitizer, debug, robinhood ON )	26m 34s
android (arm64-v8a, ON, c++_shared)	12m 56s
linux (address sanitizer, release, robinhood ON )	30m 30s
androidOnLinux	12m 6s
chromium (target_os="linux" target_cpu="x64")	8m 14s
linux (address sanitizer, release, robinhood OFF )	29m 56s
android (armeabi-v7a, OFF, c++_static)	8m 53s
chromium (target_os="android" target_cpu="arm64")	11m 20s
Ubuntu Backcompat	10m 20s
linux (thread sanitizer, release, robinhood ON )	15m 51s
mingw	9m 46s
windows (amd64)	10m 27s
windows (amd64_x86)	10m 17s
iOS	2m 56s
androidUpload	0s
windowsUpload	0s
linux Upload	0s
	3h 21m 41s

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