feat: add --debug flag to ratify CLI

[Two-Hearts]

This PR adds --debug persistent flag to ratify CLI root command.
When this flag is not set, environment variable RATIFY_LOG_LEVEL is used to set logger level.
When --debug is set, logger level is set to DEBUG.

Example usage:

ratify serve --debug ...

Resolves #1165

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (69bd336) 52.56% compared to head (7f3e0a2) 52.55%.

Files	Patch %	Lines
cmd/ratify/cmd/root.go	62.50%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1188      +/-   ##
==========================================
- Coverage   52.56%   52.55%   -0.01%     
==========================================
  Files         101      101              
  Lines        6344     6349       +5     
==========================================
+ Hits         3335     3337       +2     
- Misses       2688     2690       +2     
- Partials      321      322       +1     

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[junczhu]

LGTM

[akashsinghal]

LGTM. Thanks for adding this!

[binbin-li]

lgtm