Show pending invitations in room members list (#385)

Splits a Room's member list in 2 showing pending invitees first and then the actual room member.

This simple user facing change entails a host of under the hood changes:
- It copies the logic from the `userlist` module and merges it into the `roomdetails` module removing all details not related to the member list (e.g. gets rid of multiple selection, debouncing etc.).
- Uncouples the `roomdetails` module from the `userlist` one. Now leaving only the `createroom` module to depend on the `userlist` module. Therefore the `userlist` module could be in the future completely removed and merged into the `createroom` module.
 - Changes the room members count in the room details screen to only show the members who have joined (i.e. don't count those still in the invited state).

Missed ACs:
- This change does not make the member list live update. Discussion is ongoing on how to make this technically feasible.

Parent issue:
- https://github.com/vector-im/element-x-android/issues/246

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/room/RoomMember.kt

@@ -17,7 +17,6 @@
 package io.element.android.libraries.matrix.api.room
 
 import io.element.android.libraries.matrix.api.core.UserId
-import io.element.android.libraries.matrix.api.user.MatrixUser
 
 data class RoomMember(
     val userId: UserId,
@@ -30,12 +29,6 @@ data class RoomMember(
     val isIgnored: Boolean,
 )
 
-fun RoomMember.toMatrixUser() = MatrixUser(
-    userId = userId,
-    displayName = displayName,
-    avatarUrl = avatarUrl,
-)
-
 enum class RoomMembershipState {
     BAN, INVITE, JOIN, KNOCK, LEAVE
 }