New experimental simulation runner

[alessio]

runsim is a tool desinged to tackle issues the team at times struggle with while working with multisim.sh:

• rate limiting: by default runsim spawn min(10,len(seeds)) processes. Max number of processes can be passed via -j.
• Spawns a process each simulation and correctly repeals it upon program termination, regardless of what caused the program to terminate (SIGINT, SIGTERM, seeds exhaustion).

It must be noted that it is not fully ABI-compatible with multisim.sh:

• Different output format.
• Genesis file path must be passed via the -g flag.

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added a relevant changelog entry: sdkch add [section] [stanza] [message]
• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #4161 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #4161   +/-   ##
========================================
  Coverage    60.19%   60.19%           
========================================
  Files          212      212           
  Lines        15157    15157           
========================================
  Hits          9124     9124           
  Misses        5409     5409           
  Partials       624      624

[alexanderbez]

TestedACK, but a minor nit:

Most of the output has [Wn] as a prefix. It would be nice if the Seed n OK|FAILED also had this prefix for consistency. Would that be possible?

[sabau]

Tested locally, all good. I probably need more context about the timeline for splitting repos