Improve window caption a11y

– Ensures that the text doesn't break into multiple lines (previously hidden below the window header).
– Introduces a fade on the right edge of the window caption.
— Changes max width of the window caption.
– Changes `lineHeight` dimension unit from `dp` to `sp`.

Fix: 355522194
Fix: 356550115
Flag: com.android.window.flags.enable_desktop_windowing_mode
Test: manual – verify that window captions of Google Play Store and Reprezentacija.ba apps fade out at the edge if needed and that they are vertically centered on the window header on every possible font size available in system settings.
Change-Id: I571a0a36a5f65078966a5e7b77902ac5d6beb5fc