[Feature]: termux-app should detect phantom process killer enabled

[twaik]

Feature description

Termux app should detect phantom process killer enabled via getprop persist.sys.fflag.override.settings_enable_monitor_phantom_procs or similar commands and show prompt with these links:
#2366
https://github.com/agnostic-apollo/Android-Docs/blob/master/en/docs/apps/processes/phantom-cached-and-empty-processes.md#commands-to-disable-phantom-process-killing-and-tldr

Additional information

There are many people coming to reddit, discord and matrix with this problem, probably having some error text if termux detects "Signal 9" kill will be helpful for them.