* while executing external command, make it as foreground
* remove useless file
* add comment, make var more readable
* add comment
* fmt code
* fix windows
* fix func name
* fix clippy
* fix windows clippy
* add comments, introduce `ForegroundProcess and ForegroundChild
* fix windows clippy
* fix on windows
* no need fg_process_setup module
* Revert "no need fg_process_setup module"
This reverts commit 21ee4ffbf65df93bbc65a08a725755c081c6a0da.
* restrict visibility for helper functions