Rename BootImageModule to BootclasspathFragmentModule

Also renames files, tests, module types in a similar fashion.

There are still some references to image and boot image. They are kept
for the following reasons:
* image_name - this is the name of an ART boot image, i.e. the
  collection of .art/.oat/.vdex files.
* BootImageInfo - again this is related to the ART boot image.
* .../art_boot_images/... paths - ditto.

Bug: 177892522
Test: m nothing
Change-Id: Ie1f4738061d131fee75de48bc26a7601481bad4d

apex/apex.go

@@ -1695,7 +1695,7 @@ func (a *apexBundle) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 				}
 			case bcpfTag:
 				{
-					if _, ok := child.(*java.BootImageModule); !ok {
+					if _, ok := child.(*java.BootclasspathFragmentModule); !ok {
 						ctx.PropertyErrorf("bootclasspath_fragments", "%q is not a boot_image module", depName)
 						return false
 					}