chore: Convert to log/slog

[bhavanki]

The small amount of verbose logging in the exec command has been converted to debug logging under log/slog. Accordingly, the --verbose command line flag has been deprecated in favor of the more flexible --log-level flag.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 11.53846% with 23 lines in your changes missing coverage. Please review.

Project coverage is 36.33%. Comparing base (c02ccfc) to head (d79ef21). Report is 5 commits behind head on master.

:exclamation: Current head d79ef21 differs from pull request most recent head edec220

Please upload reports for the commit edec220 to get more accurate results.

Files with missing lines	Patch %	Lines
cmd/root.go	13.63%	19 Missing :warning:
cmd/exec.go	0.00%	4 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #519      +/-   ##
==========================================
- Coverage   36.44%   36.33%   -0.11%     
==========================================
  Files          29       29              
  Lines        3257     3275      +18     
==========================================
+ Hits         1187     1190       +3     
- Misses       1983     1998      +15     
  Partials       87       87              

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[bhavanki]

slog was introduced in Go 1.21, so this cannot be integrated yet since chamber still supports go 1.20. I'll leave this PR inactive until the 1.23 release, which is expected in August (about 2 months from now).

[kevinburkesegment]

@bhavanki Let's merge this