feat(high contrast text): update design treatment: no padding on background rects

Bug: 369901146
Flag: com.android.graphics.hwui.flags.high_contrast_text_small_text_rect
Test: atest frameworks/base/core/tests/coretests/src/android/text/LayoutTest.java
Test: atest cts/tests/tests/uirendering/src/android/uirendering/cts/testclasses/TextViewHighContrastTextTests.kt
Change-Id: Ic60172290baeef314d62c440035eb4ca00b1404a