power: Ellipsize the labels of the battery row

This helps the window fit any size, including the narrow one of phones.
7 jobs for power-panel in 3 minutes and 7 seconds
Status Job ID Name Coverage
  Build
passed #1076031
build

00:01:41

 
  Test
passed #1076032
test

00:01:25

 
  Manual
manual #1076034
asan allowed to fail manual
asan
manual #1076033
allowed to fail manual
flatpak
manual #1076037
allowed to fail manual
msan
manual #1076035
allowed to fail manual
tsan
manual #1076036
allowed to fail manual
ubsan