Fix: refactor duplication scripts

[jluque0101]

---

Note

Centralizes common logic and simplifies the release/changelog workflow.

• New utils.sh provides shared configure_git, checkout_or_create_branch, push_branch_with_handling, and create_pr_if_not_exists helpers
• New update-release-changelog.sh generates changelog (with --requirePrNumbers), derives version/branch when needed, avoids no-op PRs, and supports optional inputs (previous_version_ref, custom changelog branch, explicit version)
• create-platform-release-pr.sh now sources utils.sh, respects BASE_BRANCH when creating the release branch, delegates changelog creation to update-release-changelog.sh, and passes git identity via env
• Minor robustness improvements: whitespace-trimmed params, explicit git config args, safer remote branch detection/fetching for previous version refs, and skipping version-bump PRs on hotfixes

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