[Feature] Add global setting to make getByText default to exact: true

[The default behaviour in Testing Library is `{ exact: true }`](https://testing-library.com/docs/queries/bytext), while Playwright defaults to `{ exact: false }`.

Naturally this is bound to catch people out. It would be useful to have at least a global setting to change the default to `{ exact: true }`.

See also https://github.com/microsoft/playwright/discussions/18239

Start by reviewing the getByText implementation and the linked Testing Library documentation, then read the related Playwright discussion for prior design context. Done means Playwright provides a global setting that makes getByText default to exact: true without requiring the option on every call.

Written by the indexing model from the issue text.