Add two complex scripts as integration tests

[dspinellis]

• Draw the Mandelbrot set.
• Create a waveform of Bach's Prelude.

Both were obtained from https://github.com/laserbat. The interpreter of brainfuck written entirely in sed wasn't added, because the two layers of obfuscation (sed script and brainfuck program) would make any divergence difficult to debug.

Both tests take long to run, so they are ignored by default.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.15%. Comparing base (3479e9b) to head (e40ddb1).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #241   +/-   ##
=======================================
  Coverage   82.15%   82.15%           
=======================================
  Files          13       13           
  Lines        5324     5324           
  Branches      293      293           
=======================================
  Hits         4374     4374           
  Misses        948      948           
  Partials        2        2           

Flag	Coverage Δ
macos_latest	82.59% <ø> (ø)
ubuntu_latest	82.71% <ø> (ø)
windows_latest	0.00% <ø> (ø)

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