fix(flag): resolve env's from config file for string and []string flags

[DmitriyLewen]

Description

See #8436

Example:

cache:
  dir: "$HOME/.cache/trivy"

Before:

2025-02-24T11:48:13+06:00       DEBUG   Cache dir       dir="$HOME/.cache/trivy"

After:

2025-02-24T11:47:23+06:00       DEBUG   Cache dir       dir="/Users/dmitriy/.cache/trivy"

Related issues

• Close #XXX

Related PRs

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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).

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