Screen Resolution: add space for 4-digit values

Add logic that composes screen resolution string with non-breaking
spaces. Now setting page will show "1 080 x 1 280" instead of "1080 x
1280"

Test: atest -c <SETTINGS_APP_PATH>/tests/unit/src/com/android/settings/display/ScreenResolutionFragmentTest.java
Test: verified on device
Flag: EXEMPT no API change
Bug: 385895191
Change-Id: I9a4bbd7c20e8c700dee6e997a36d4fda69f4d780