fix(flag): skip hidden flags for --generate-default-config command

[DmitriyLewen]

Description

Currently we include all flags in the default config.
But Trivy returns an error for removed flags.

Unfortunately viper has no options to remove flags, so we need to reset viper and add the required flags to --generate-default-config

Before:

➜  trivy image --generate-default-config && cat trivy-default.yaml | grep reset
2024-12-04T17:35:49+06:00       INFO    Writing the default config to trivy-default.yaml...
    reset-checks-bundle: false
reset: false

After:

➜  ./trivy image --generate-default-config && cat trivy-default.yaml | grep reset
2024-12-04T17:36:18+06:00       INFO    Writing the default config to trivy-default.yaml...

Related issues

• Close bug: config file generated by --generate-default-config contains removed and deprecated flags #8043

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).