Merge develop into the PreviewParam rename

The 174 commits develop gained since this branch was cut touch preview data
in three ways, and each is resolved so the flipped konsist rule still holds
across the merged tree.

Two screens the branch had renamed were deleted upstream by "Remove the
account provider search screen and homeserver resolver": the
changeaccountprovider and searchaccountprovider packages. Their deletion
wins, so ChangeAccountProviderStatePreviewParam, SearchAccountProviderStatePreviewParam
and the two views that used them go with them rather than coming back
under the new name.

Two preview classes develop added still carried the old suffix and are
renamed here, along with the `@PreviewParameter` reference in each view:
GlobalSearchStateProvider -> GlobalSearchStatePreviewParam and
SendFailureDialogStateProvider -> SendFailureDialogStatePreviewParam.

Everything else merged textually. No production class extending
PreviewParameterProvider is left with a `Provider` name, and no reference
to any of the 194 renamed names survives outside the CHANGES.md entry that
records a past pull request title.

AGENTS.md

@@ -39,6 +39,7 @@ PRs must meet these rules.
 - Use `@PreviewsDayNight` for consistency.
 - Use `PreviewParameterProvider` (e.g., `FooStatePreviewParam`) to provide states.
 - Wrap previews in `ElementPreview { ... }`.
+- When writing tests, never try to record the screenshots, the CI will do it.
 
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