Fix drawable-state cache expired issue

Context:
  The list of Preloaded drawables is defined in
  /system/framework/framework-res.apk. It describes a set of
  drawables to be loaded as the cache. The cache includes the
  drawables states for each preloaded drawable.

  For example: we have preloadSet(
          res/drawable/a.png
          res/drawable/b.png
          res/drawable/c_vector_drawable.xml).
  Because both of loading png and decoding xml to be a vector
  drawable take I/O and parsing time, in order to prevent app
  processes from doing again, the drawable state describes where is
  the decoded image of Bitmap in memory and the data structure of
  VectorDrawable.

  When some process wants to load R.drawable.a, it intends to load
  res/drawable/a.png, it's already in the cache because Zygote has
  preloaded as the drawable state for res/drawable/a.png. The
  Resources clones another drawable state and creates a new Drawable
  instance back to the app.

Solution:
  ResourcesPerfWorkloads sets a special version of the framework
  resources package but it doesn't rebuild the drawable state cache
  according to the special framework resources package.

  When the drawable state cache belonging to the old framework
  resources package doesn't match the new framework resources
  package, accessing the preloaded drawables may trigger this kind
  of issue.

  The solution is to clear the static caches in ResourcesImpl and
  load the cache defined in the specified framework resources
  package.

This patch also moves the preload resources tasks from ZygoteInit.java
to Resources.java.

Bug: 193826688
Test: atest ResourcesPerfWorkloads

Change-Id: I0fa25612bf82dd810d1d9443068a9a302a61d53d