Only dump necessary info when specifying a package

Revise the logic of dump to drop unnecessary sections that aren't
relevant to the given package name. Besides, align the style of
each logic block.

Fix: 187415768
Test: manually check the result of 'dumpsys package' whether:
      1. any section that has data relevant to the given package
         name is missing.
      2. print 'Unable to find package' when the given package
         name doesn't exist.
Change-Id: Ide350d2b303fe6536ebd75e3bf7d7c9f54f4e0dd