scripts: west: fix some intel_s1000 runner issues
scripts: west: fix some intel_s1000 runner issues

There are a few issues with the intel_s1000 runner:

- it doesn't attach to the client when running debug (this is
  a part of the command's contract specified in core.py)

- it uses hard-coded sleeps when running subprocesses instead of
  waiting for them to terminate

- it re-implements pre-existing popen_ignore_int() functionality (in a
  way that is not portable to Windows) rather than using it directly

Fix these issues.

Signed-off-by: Marti Bolivar <fd5da480b758a78208111e6ae5c6806e1f887137@opensourcefoundries.com>

zephyriot/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,zephyriot/zephyr,ldts/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,galak/zephyr,mbolivar/zephyr,ldts/zephyr,explora26/zephyr,ldts/zephyr,nashif/zephyr,zephyriot/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,finikorg/zephyr,kraj/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,punitvara/zephyr,Vudentz/zephyr,zephyriot/zephyr,punitvara/zephyr,Vudentz/zephyr,kraj/zephyr,punitvara/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,mbolivar/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,mbolivar/zephyr,Vudentz/zephyr,ldts/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,kraj/zephyr,punitvara/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,nashif/zephyr,nashif/zephyr,punitvara/zephyr,finikorg/zephyr