Combine docs-builder bundle prs and prs-file options

[lcawl]

This PR alters #2341

Summary

Combined the --prs and --prs-file options for the docs-builder changelog bundle command.
The --prs option now accept multiple occurrences, where each occurrence can be either comma-separated PRs or a file path.

Changes Made

• ChangelogCommand.cs:
  • Removed the --prs-file parameter and updated the --prs parameter documentation to indicate it can accept either PRs or a file path.
  • Added logic to process each --prs occurrence:
    • If it contains commas, split by comma and add each as a PR
    • If it's a single value, pass it as-is (handled by the service layer as file path or PR)
• ChangelogService.cs: Updated the logic to detect if --prs contains a file path
• ChangelogBundleInput.cs: Removed the PrsFile property since it's no longer needed.
• Documentation: Updated both docs/cli/release/changelog-bundle.md and docs/contribute/changelog.md to reflect the combined option.
• Tests: Updated tests to use the new Prs property instead of PrsFile.

Behavior

--prs "https://github.com/owner/repo/pull/123,12345" - Comma-separated PRs in one occurrence
--prs /path/to/file.txt - File path in one occurrence
--prs "https://github.com/owner/repo/pull/123,12345" --prs /path/to/file.txt - Multiple occurrences, combining both formats

Notes:

• Each --prs occurrence is processed independently
• Comma-separated values within an occurrence are split into individual PRs
• File paths are detected and handled by the service layer
• All existing tests pass

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

3. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used: composer-1 agent