Create booleans to configure preferences (settings screens) easily

Create a set of booleans to configure preferences screens easily. It also has the advantage to centralize the default value for each setting. Before 2 boolean values had to be changed to change the default value of a preference (one in the XML and one in the file VectorPreferences.kt).

There is now a boolean to show or hide the setting in the preference screen, and a boolean for the default value of the preference.

It has been done for the root preference screen and the message bubbles: see [here](https://github.com/vector-im/element-android/blob/develop/vector-config/src/main/res/values/config-settings.xml#L29) and the PR #5157 for more details.

Now we should do it for every single preference, which is, let's be honest, a boring and fastidious work.

If anyone in the community wants to give us a hand, it will be appreciated. It can of course be split into several small PRs (say one PR per preference screen). Every small PR will be appreciated!