SystemUI: Status bar clock - fixes

This commit fixes:

- no overlapping more from status bar icons on center clock.
  The width depending on what the user has setuped (date and clock) is exactly meassured now
- do not start animations if they are not needed
- reduce settings provider calls
- a bit cleanup

Change-Id: I7a37a6ae8f9bad0f265119af05dc20cf21cd6890

(cherry picked from commit 7edabdcc95168f5a41b6a66ed538b4da3266a58d)

(cherry picked from commit 1e49a0d5bca062daf46c53e4cddebc854520a43c)

(cherry picked from commit 6b3ae04e36351b65e5d57ebf6db4a51f3b72e7ab)
SystemUI: Ensure that the Clock is actually enabled in IconMerger

to device if we need to calculate

Change-Id: If12b0e26b32f044f1a82cf8b539283194d1d0b4c

(cherry picked from commit d47e8f6a27d7d9a72ca65f13c9c3971bdbc262a4)

(cherry picked from commit 50853e5afc6c228d0c523b47aa85a5d4a8400847)

(cherry picked from commit 2d103f44454aeade2df78bfdf087c5caadeaa03c)