194 expand shell command to return exit code and stderr

[hulto]

What type of PR is this?

/kind cleanup
/kind documentation

What this PR does / why we need it:

Adds stderr and status code to the output of exec and shell to provide better insight into run tasks.
The result is returned as a dictionary:

{
    "stdout":"root\n",
    "stderr":"",
    "status":0,
}

Which issue(s) this PR fixes:

Fixes #194

[codecov]

Codecov Report

Merging #209 (9a1a0fa) into main (26ff8be) will decrease coverage by 0.08%.
The diff coverage is 85.48%.

@@            Coverage Diff             @@
##             main     #209      +/-   ##
==========================================
- Coverage   72.42%   72.35%   -0.08%     
==========================================
  Files          82       82              
  Lines        4617     4666      +49     
==========================================
+ Hits         3344     3376      +32     
- Misses       1188     1205      +17     
  Partials       85       85              

Impacted Files	Coverage Δ
implants/eldritch/src/sys/exec_impl.rs	83.01% <62.50%> (-13.41%)	⬇️
implants/eldritch/src/sys/shell_impl.rs	95.78% <96.15%> (-1.27%)	⬇️
implants/eldritch/src/lib.rs	93.58% <100.00%> (ø)
implants/eldritch/src/sys.rs	57.77% <100.00%> (ø)
implants/imix/src/main.rs	77.77% <100.00%> (ø)

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[Cictrone]

it fails D:

[Cictrone]

Blorp