Fix "App wastes CPU resources while playing video"

Use fixed size (half of screen) for each TextView
Fixes #2529
This modification also improve overall UI performance. #2528
UI appearing time (landscape orientation, video paused, v3.5.0):
Samsung Note 4, Android 6.0.1 (debug). Was ~300 ms if I disable animation. Now it ~65 ms.
Samsung Note 4, Android 6.0.1 (release). Was ~1450 ms if I disable animation. Now it ~350 ms.
Lenovo P2a42. Android 6.0.1 (release). Was ~130 ms if I disable animation. Now it ~55 ms.
Xiaomi 11T, Android 12 (release). Was ~100 ms if I disable animation. Now it ~40 ms.