Add JSON format for list outputs

[PrzemyslawKlys]

📖 Description

Adds --format json support for package listing output.

This enables machine-readable output for:

• winget list --format json
• winget upgrade --format json when used in list-only mode

The default table output is unchanged.

The JSON output includes installed package fields that match the existing list and upgrade table data, including package name, id, installed version, available version, and source. It also keeps JSON parseable for empty results and common error paths such as source-open failures, WinGet policy blocks, and generic execution failures.

winget upgrade --format json is intentionally limited to non-mutating upgrade listing. Commands such as winget upgrade --all --format json are rejected so package installation progress is not mixed with structured output.

🔗 References

Related to #1753.

🔍 Validation

Added focused test coverage for:

• JSON list output
• JSON upgrade-list output
• empty result output
• settings warnings before JSON output
• source-open failures
• WinGet policy blocks
• generic execution failures
• preserving help output for --format json --help
• rejecting JSON output for unsupported upgrade execution modes
• rejecting --details with JSON list output

Ran the focused AppInstallerCLITests scenarios for the JSON list and upgrade flows locally.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated Release Notes (if applicable)
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)

📋 Issue Type

• Bug fix
• Feature
• Task

Microsoft Reviewers: Open in CodeFlow