What?

This adds locator.locator nesting.

Why?

It allows us to define locators relative to a parent locator e.g.:

await page
  .locator('[data-testid="inventory"]')
  .locator('[data-item="apples"]')
  .locator('button.add')
  .click();

Without this, there is no way to perform such a nesting. This functionality will be more useful once we start to implement APIs that require such nesting, such as locator.getBy*.

Checklist

• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added tests for my changes.
• I have run linter and tests locally (make check) and all pass.

Checklist: Documentation (only for k6 maintainers and if relevant)

Please do not merge this PR until the following items are filled out.

• I have added the correct milestone and labels to the PR.
• I have updated the release notes: link
• I have updated or added an issue to the k6-documentation: Add locator.locator doc for k6 browser k6-docs#2050
• I have updated or added an issue to the TypeScript definitions: grafana/k6-DefinitelyTyped@c61e951

Related PR(s)/Issue(s)

#5030