Bring back "show whitespace characters" in Pull Request view

Original description:

Hello,

With the release of 7.0, you can no longer show whitespace characters in Pull Request view. It is possible to show them BEFORE making a pull request.

@mad from the Atlassian Team confirmed that this was removed. See post below:
https://community.atlassian.com/t5/Bitbucket-discussions/Bitbucket-7-Pull-Request-changes-no-longer-show-whitespace/m-p/1320132#M2586%3Futm_source=atlcomm&utm_medium=email&utm_campaign=mentions_reply&utm_content=topic

Please bring this option back, as it is crucial in ensuring whitespace consistency.

Thank you.