Fix DemoMode icon spacing

- Use the same margin on the left of Wi-Fi (2.5dp)
- DemoMode uses the padding of the view it's replacing, and WRAP_CONTENT
for the width of its children
- Fix DemoMode etc dot color
- Don't constrain number of icons if DemoMode is replacing an
unconstrained container

Test: visual;
adb shell settings put global sysui_demo_allowed 1 && \
adb shell am broadcast -a com.android.systemui.demo -e command clock -e hhmm 0900 && \
adb shell am broadcast -a com.android.systemui.demo -e command network -e wifi show -e level 4 && \
adb shell am broadcast -a com.android.systemui.demo -e command network -e mobile show -e datatype none -e level 4 && \
adb shell am broadcast -a com.android.systemui.demo -e command status -e bluetooth disconnected && \
adb shell am broadcast -a com.android.systemui.demo -e command battery -e level 100 -e plugged false

Change-Id: I1d1389f9c6d6cb7d6078af5bbe4bc21e42771560
Fixes: 79094455