Space Switching: Add Space List Bottom Sheet

[ericdecanini]

We must create a bottom sheet with all the spaces and subspaces a user is in, much like the current room list.

Figma design link: https://www.figma.com/file/Hw4gjP3pknMZUir8jQqmWH/%5BMobile%5D-IA-early-proposals?node-id=2523%3A135211

The bottom sheet should be opened by a secondary FAB and should contain only the direct child spaces of the current spaces (or the root spaces if not currently in a space)

Not included in this issue:

• Toolbar changing text based on spaces switched
• Header text in bottom sheet being updated with hierachy of spaces
• Back and up navigation between spaces
• Empty states

Known bugs to be addressed separately:

• Sometimes the bottom sheet opens with the wrong size

Parent epic: https://github.com/vector-im/element-android/issues/6605