28936 [web] reuse browser instance across screenshot tests (cla: yes, platform-web, needs tests)

28937 Cherry-pick #28846 and #28743 into flutter-2.6-candidate.11 (platform-ios, platform-android, cla: yes, needs tests, embedder)

28951 [fuchsia] Pass WeakPtrs to GfxConnection FIDL fns. (cla: yes, waiting for tree to go green, platform-fuchsia, needs tests)

28965 Roll CanvasKit to 0.30 (cla: yes, platform-web, needs tests)

28970 [Windows] Add restart hooks, and reset keyboard (cla: yes, platform-windows, needs tests)

28977 Remove some deprecated APIs from the Android embedding (platform-android, cla: yes, waiting for tree to go green, needs tests)