fix(high contrast text): fix text cursor, spellcheck, etc not visible

Since we now draw a solid background rectangle behind the text, the
background draws over the text position cursor, underline squiggles for
spelling errors, etc.

To fix this, we just draw those things on top of all the text, its
background, and selection highlights.

Bug: 186567103
Flag: ACONFIG com.android.graphics.hwui.flags.high_contrast_text_small_text_rect TEAMFOOD
Test: atest core/tests/coretests/src/android/text/LayoutTest.java
Test: manual
1. adb shell setenforce 0 && adb shell setprop persist.device_config.aconfig_flags.accessibility.com.android.graphics.hwui.flags.high_contrast_text_small_text_rect true && adb shell stop && adb shell start
2. Settings -> Accessibility -> Display Size and Text
3. Turn on High Contrast Text
4. Blinking cursor and error squiggles should be visible.

Change-Id: I367ffcbdfc3ca35f15679fac06fa8c03309facd3