add: cookie functions to Bruno scripts

[pooja-bruno]

Description

Added cookie helper functions to Bruno scripts via the bru.cookies API. This provides similar functionality to Postman's pm.cookies API, making it easier for users to work with cookies in their scripts.

Features added:

• bru.cookies.get() - Returns all cookies as an object
• bru.cookies.get("cookieName") - Gets a specific cookie by name
• bru.cookies.has("cookieName") - Checks if a specific cookie exists

Contribution Checklist:

• [x] The pull request only addresses one issue or adds one feature.
• [x] The pull request does not introduce any breaking changes
• [ ] I have added screenshots or gifs to help explain the change if applicable.
• [x] I have read the contribution guidelines.
• [x] Create an issue and link to the pull request.

Note: Keeping the PR small and focused helps make it easier to review and merge. If you have multiple changes you want to make, please consider submitting them as separate pull requests.

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