Migration to Element X - add banner in room list.

[bmarty]

Type of change

• Feature
• Bugfix
• Technical
• Other : help user to migrate to Element X

Content

Add a banner on the room list to advertise Element X in Element Classic.

• A milestone is defined in the code: 15th of November.
• The banner configuration is read from the .well-known file
• When configuration is missing, the banner is not displayed before 15th of November and displayed after.
• When the configuration is present, the banner is displayed according to the configuration.
• When the user closes the banner, it will be displayed again (if the configuration / date allow it) 7 days later.

The banner will be displayed only if not disabled in the .well-known file.

This PR also introduce a change in the cache, to avoid trying to fetch a non existing .well-known file each time the application is resumed. A check will occur only after a 8 hours delay instead.

Motivation and context

Help user migrate to Element X

Closes #9169
Closes #9170
Closes #9171

Screenshots / GIFs

Tests

• on matrix.org, no change should be visible before 15th of November.
• else user can setup a .well-known file to tweak the banner behavior. Be aware of the 8 hours cache of this file.

Tested devices

• Physical
• Emulator
• OS version(s):

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/element-hq/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()