feat(client-core): add signal option to support abort fetch

[woai3c]

Check List

• Tests have been run in packages where changes made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Description of Changes Made

This PR adds the ability to abort requests in @cubejs-client/core by introducing support for the AbortController signal. The implementation:

1. Extends the HttpTransport constructor and request method to accept a signal parameter
2. Adds signal support to CubeApi's constructor and all request methods (load, meta, sql, dryRun)
3. Implements priority handling where method-specific signals override constructor signals
4. Adds comprehensive test coverage for all signal-related functionality

These changes allow users to cancel in-flight requests by using the AbortController API:

// Example usage
const controller = new AbortController();
const { signal } = controller;

// Pass signal in constructor (affects all requests)
const cubeApi = new CubeApi('token', {
  apiUrl: '...',
  signal
});

// Or pass signal to specific methods
const resultSet = await cubeApi.load(query, { signal });

// To abort the request at any time
controller.abort();