Adapt HealthChat to upstream v26.10.0

Follow-ups needed after rebasing the HealthChat series from v26.07.0 onto
v26.10.0 that span several of the replayed commits:

- Rename the five PreviewParameterProvider subclasses in features/healthchat
  to the *PreviewParam suffix now enforced by Konsist.
- Rename MemberDirectoryEvents and HealthChatProfileSectionEvents to the
  *Event suffix used by every upstream sealed interface.
- Import FakeStartDMAction from features/startchat/test, where it lives now.
- ListItem lost its headlineContent parameter in favour of content.
- HomeView gained onAddAccountClick and onSwitchToAccount, and onRoomClick
  now carries an EventId; update HomeViewBackHandlingTest accordingly.
- Restore upstream's codecov-action pin (v7.1.1) that the CI squash carried
  back to v7.0.0.
- Gate the new pr-checks.yml on the upstream repository: this fork does not
  use the PR- label convention.
- Add the 26.10.0 section to HEALTHCHAT_CHANGES.md.

features/home/impl/src/test/kotlin/io/element/android/features/home/impl/HomeViewBackHandlingTest.kt

@@ -28,8 +28,10 @@ class HomeViewBackHandlingTest : RobolectricTest() {
                     currentHomeNavigationBarItem = HomeNavigationBarItem.Members,
                     eventSink = eventsRecorder,
                 ),
-                onRoomClick = {},
+                onRoomClick = { _, _ -> },
                 onSettingsClick = {},
+                onAddAccountClick = {},
+                onSwitchToAccount = {},
                 onSetUpRecoveryClick = {},
                 onConfirmRecoveryKeyClick = {},
                 onStartChatClick = {},
@@ -58,8 +60,10 @@ class HomeViewBackHandlingTest : RobolectricTest() {
                     currentHomeNavigationBarItem = HomeNavigationBarItem.Members,
                     eventSink = eventsRecorder,
                 ),
-                onRoomClick = {},
+                onRoomClick = { _, _ -> },
                 onSettingsClick = {},
+                onAddAccountClick = {},
+                onSwitchToAccount = {},
                 onSetUpRecoveryClick = {},
                 onConfirmRecoveryKeyClick = {},
                 onStartChatClick = {},