kernel: remove become_manager and minor refactors #205

Job	Run time
build-kernel (android-14-avd_x86_64, android-14-avd_x86_64.xml, x86_64) / Build android-14-avd_x86_64	29m 44s
build-kernel (android-15-avd_aarch64, android-15-avd_aarch64.xml, aarch64) / Build android-15-avd_aarch64	33m 20s
	1h 3m 4s

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