[ESD-10361] Fix password strength popup overflow issue

[stevehobbsdev]

Changes

This PR provides a host of CSS fixes that fix a number of issues, mainly the password strength popup issue:

• The password strength popover not being able to properly overflow the primary
  container. In order to fix this, a host of CSS changes were made, which also fixed the other issues below.
• Removes the need for the dynamically-calculate header
• Fixes the content popping out of the bottom of the container on small screen
  heights
• Removes the need for overflow-x: auto which caused rendering issues

I've also adding some instructions about testing a local Lock build through the ULP.

Screenshots highlight the issue with the password strength popover. Might be hard to see given the background, but the top of the popover is clipped against the top of the Lock widget in the before screenshot.

Before

After

Testing

This was manually tested in all the browsers I can think of, in mobile and desktop view:

• Firefox 83 on Windows

• Edge 87 on Windows

• IE 11 on Windows 10

• Chrome on Samsung Galaxy S10

• Chrome on Google Pixel 3

• Safari on iPhone 11 (iOS 14, simulator)

• Safari on iPhone 8 (iOS 12, simulator)

• This change adds unit test coverage

• This change adds integration test coverage

• This change has been tested on the latest version of the platform/language

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors
• All code quality tools/guidelines have been run/followed
• All relevant assets have been compiled
• All active GitHub checks have passed