Refactor library path representation in dexpreopt.

This is a preliminary CL before fixing on-device paths to DEX jars.
It groups together the inormation about on-host build paths and
on-device install paths to library DEX jars.

This CL changes the structure of module dexpreopt.config files
generated by the build system. Aside of that, no functional changes.

Test: lunch aosp_cf_x86_phone-userdebug && m
Change-Id: I059654be7670f2ba66248d9c49b9694a0591f9c1

java/dexpreopt.go

@@ -37,7 +37,7 @@ type dexpreopter struct {
 	usesLibs         []string
 	optionalUsesLibs []string
 	enforceUsesLibs  bool
-	libraryPaths     map[string]android.Path
+	libraryPaths     dexpreopt.LibraryPaths
 
 	builtInstalled string
 }