adds flag for saving report toml to back build and rebase

[joe-kimmel-vmw]

Summary

Adds a --report-output-dir flag to both build and rebase commands. If that flag is present then we will write the report.toml file which contains valuable metadata in a friendly format.

Output

Before

this "before" snapshot includes absolutely zero report.toml files:

> pack build ...
> ls
[observe the complete and utter lack of report.toml]

After

> pack build ... --report-output-dir `pwd`
> ls
[gaze upon my report.toml file, ye mighties, and despair! Or rejoice, whatevs really but rejoicing is more fun]

(and similar for rebase)

Documentation

• Should this change be documented?
  • Yes, see <-- Hey it looks like pack cli flags are auto-documented? So that'll kinda take care of itself after this is released and the docs are regenerated with that version of pack?
  • No

Related

Resolves #1221
Resolves #1565

[codecov]

Codecov Report

Merging #1598 (ac117c3) into main (d1024e9) will decrease coverage by 0.04%.
The diff coverage is 85.46%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1598      +/-   ##
==========================================
- Coverage   80.61%   80.58%   -0.03%     
==========================================
  Files         156      156              
  Lines       10455    10480      +25     
==========================================
+ Hits         8427     8444      +17     
- Misses       1528     1534       +6     
- Partials      500      502       +2     

Flag	Coverage Δ
os_linux	79.33% <85.46%> (-0.02%)	⬇️
os_macos	77.43% <85.46%> (-0.02%)	⬇️
os_windows	80.49% <85.46%> (-0.02%)	⬇️
unit	80.58% <85.46%> (-0.03%)	⬇️

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