Collect more stats

[asmacdo]

• Collects average usages
• reports absolute values for memory
• reports number of datapoints (reports)
• reports number of samples

Fixes: #63
Fixes: #41

$ duct --s-i 1 --r-i 2 -p ZZZZ_  --clobber ./test/data/test_script.py --duration 10 --memory-size 1000
duct is executing ./test/data/test_script.py --duration 10 --memory-size 1000...
Log files will be written to ZZZZ_
this is of test of STDERR
this is of test of STDOUT
Test completed. Consumed 1000 MB for 10 seconds with CPU load factor 10000.

Exit Code: 0
Command: ./test/data/test_script.py --duration 10 --memory-size 1000
Log files location: ZZZZ_
Wall Clock Time: 10.366 sec
Memory Peak Usage (RSS): 1036000 KiB
Memory Average Usage (RSS): 1036000.000 KiB
Virtual Memory Peak Usage (VSZ): 1258432 KiB
Virtual Memory Average Usage (VSZ): 1258432.000 KiB
Memory Peak Percentage: 3.1%
Memory Average Percentage: 3.100%
CPU Peak Usage: 100.0%
Average CPU Usage: 99.780%
Samples Collected: 10
Reports Written: 6

[codecov]

Codecov Report

Attention: Patch coverage is 98.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.90%. Comparing base (eb1237c) to head (97ea981).
Report is 2 commits behind head on main.

Files	Patch %	Lines
src/duct/__main__.py	98.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #104      +/-   ##
==========================================
+ Coverage   92.47%   93.90%   +1.42%     
==========================================
  Files           2        2              
  Lines         319      361      +42     
  Branches       50       55       +5     
==========================================
+ Hits          295      339      +44     
+ Misses         18       16       -2     
  Partials        6        6              

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[asmacdo]

The print statements have gotten to be quite messy, and this PR makes it worse, but I'll refactor that in #64

[asmacdo]

@jwodder do you want another look are am I good to merge?