Introduce a StartChatFlowCoordinator instead of handing a navigation stack to the Screen Coordinator. (#4674)

* Introduce a basic StartChatFlowCoordinator.

* Move the rest of the start chat flow from the screen coordinator into the flow coordinator.

* Add a UI test for the entire start chat flow.

* Refactor CreateRoom… to CreateRoomScreen…

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-iPad-en-GB.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:e1624d4be85be4801b7a407ed8d09c815d98b1eb4422d4fc8095795e3a73cd17
-size 144918
+oid sha256:27b070d92b8846ab416aeb3964d3b698b15aae6a6a5e03f103546bc00b57a291
+size 144359

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-iPad-pseudo.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:5d668d5fd1d22b0fc782dcf22c1d674fae87d61b289451887e48011ea2c288a9
-size 173173
+oid sha256:96418567c90c7e7a42b4a7129cc803ce0f50de55cb14021fe8c9b5042810c4e4
+size 171338

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-iPhone-16-en-GB.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:8e3e2883875feedec7a243f676918e3d6f4d05826702a8f2c2807fc5a0bc7bdf
-size 96282
+oid sha256:209bc72d50cf549621b1bb690349290aa9f12fd79501cc3089b1dc0a525495c2
+size 95602

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-iPhone-16-pseudo.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:fd0da3fb9239fe4f131b4a19057bd49bda67b72ba7caf17d8f86cb9f6a239fc0
-size 125320
+oid sha256:a9f24fc08ec1f408042f6311ddada15f01413f93806bba7742b417743c8cf011
+size 125251

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-without-users-iPad-en-GB.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:27b070d92b8846ab416aeb3964d3b698b15aae6a6a5e03f103546bc00b57a291
-size 144359

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-without-users-iPad-pseudo.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:96418567c90c7e7a42b4a7129cc803ce0f50de55cb14021fe8c9b5042810c4e4
-size 171338

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-without-users-iPhone-16-en-GB.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:209bc72d50cf549621b1bb690349290aa9f12fd79501cc3089b1dc0a525495c2
-size 95602

PreviewTests/Sources/__Snapshots__/PreviewTests/createRoom.Create-Room-without-users-iPhone-16-pseudo.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:a9f24fc08ec1f408042f6311ddada15f01413f93806bba7742b417743c8cf011
-size 125251