test: simpler killing of running simulators

[raphinesse]

Motivation and Context

Slim down code base

Description

This replaces a JS script that should kill any running simulators by a simple shell command

Testing

• I verified that the killall command does nothing if no simulator is running
• It would be great if someone verified that this actually kills a running simulator

[codecov-commenter]

Codecov Report

Merging #1179 (8dc9228) into master (b0d7099) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1179   +/-   ##
=======================================
  Coverage   74.95%   74.95%           
=======================================
  Files          14       14           
  Lines        1705     1705           
=======================================
  Hits         1278     1278           
  Misses        427      427           

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