Add nested array and nested map to stress test program

[fxamacker]

Closes #157

Description

Update stress test program to

• add nested array and nested map
• add slab health check
• use prng that isn't shared with other packages
• seed new prng with time.Now().UnixNano() by default
• add command line flag to optionally specify a seed, minheap, and maxheap
• print the seed in case we want to rerun tests with it
• increase frequency of random set vs random remove to get higher number of elements
• for array, use 2000 MiB as MaxArrayHeapAlloc. When reached, remove until MinArrayHeapAlloc is reached (1000 MiB).
• for map, use 2000 MiB as MaxMapHeapAlloc. When reached, remove until MinMapHeapAlloc is reached (1000 MiB).
• clear read and write caches when array or map is empty while heap usage is still too high, then call runtime.GC()

Command line flags

Adding new elements outpaces random removal of elements. The maxheap flag is used to prevent the program from using up all available memory.

During random ops, HeapAlloc will eventually reach/exceed maxheap, causing random elements to be removed until minheap is reached before resuming.

% ./stress -h
Usage of ./stress:
  -maxheap uint
        max HeapAlloc in MiB to trigger extra removal of elements (default 2000)
  -maxlen uint
        max number of elements (default 10000)
  -minheap uint
        min HeapAlloc in MiB to stop extra removal of elements (default 1000)
  -seed string
        seed for prng in hex (default is Unix time)
  -type string
        array or map (default "array")            

Caveats

• Number of elements printed refers to top-level elements only. It doesn't count nested elements.
• This program can use up several GB of RAM when running, depends on maxheap flag (2000 MiB by default).
• This program is not yet usable in CI (need to have timeout flag as an option, non-zero exitcode on error, etc).
• This program isn't a fuzz test, so there's no corpus being built that can be used to reduce duration of future runs. So this stress test should be run for a long duration every time.

  ---

• [x] Targeted PR against main branch
• [x] Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• [x] Code follows the standards mentioned here
• [x] Updated relevant documentation
• [x] Re-reviewed Files changed in the Github PR explorer
• [x] Added appropriate labels

[codecov-commenter]

Codecov Report

Merging #231 (92255df) into main (d9e6627) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #231   +/-   ##
=======================================
  Coverage   68.60%   68.60%           
=======================================
  Files          14       14           
  Lines        7129     7129           
=======================================
  Hits         4891     4891           
  Misses       1611     1611           
  Partials      627      627           

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update d9e6627...92255df. Read the comment docs.

[fxamacker]

Need to make some more changes before merging.

[turbolent]

👏

[turbolent]

Smart to test until a certain memory threshold is reached and pruning to keep testing 👍