Implement new rule no-duplicate-imports

[ajafff]

PR checklist

• Addresses an existing issue: New rule: no-duplicate-imports #2869
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

[new-rule] no-duplicate-imports
Fixes: #2869

Is there anything you'd like reviewers to focus on?

Some thoughts about the current implemenation:

• There no option includeExports like in the ESLint rule. Do we want this?
• ImportEqualsDeclarations are ignored
• There's no fixer. That can be added later.
• In some cases you cannot simply merge imports. The rule will still complain about them (maybe the error message should be changed?):

import foo from 'foo';
import foo2 from 'foo'; // cannot be combined with preceding import

import * as bar from 'bar';
import {baz} from 'bar'; // cannot be combined with preceding import

CHANGELOG.md entry:

[adidahiya]

In some cases you cannot simply merge imports. The rule will still complain about them (maybe the error message should be changed?)

👍 for still complaining about them. same error message is fine for now