Add client roots addition/removal API and listRoots handler

[ptitjes]

This PR add support for adding/removing client roots and handling listRoots requests.

Fixes #106

Motivation and Context

There is currently no APIs to handle roots.

How Has This Been Tested?

I added tests to ClientTest, for:

• adding and removing roots
• checking the client receives and handles server's roots list requests
• checking roots list changed notifications

Breaking Changes

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

N/A

[Copilot]

Pull Request Overview

This PR adds client roots management functionality including APIs to add, remove, and list roots, along with corresponding tests.

• Introduces new roots management methods (addRoot, addRoots, removeRoot, removeRoots, and sendRootsListChanged) in the Client class.
• Adds tests to verify roots addition, removal, error throwing when capability is unsupported, and roots list changed notifications.
• Updates the SDK API definitions with the new methods.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/jvmTest/kotlin/client/ClientTest.kt	Added tests to verify clients' roots API operations
src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/Client.kt	Implements roots management functionality and internal handlers for listRoots
api/kotlin-sdk.api	Updates API definitions to include the new roots methods

[ptitjes]

@e5l Hi! I rebased this PR on main. Is there anything else I should do to get this approved and merged?