Make DexOptHelper.forceDexOpt a legacy dexopt only method.

This change also moves the declaration of these two methods from
the IPackageManager interface to the PackageManagerInternal interface
because IPackageManager is in f/b/core and therefore cannot access
LegacyDexoptDisabledException.

Test: adb shell pm force-dex-opt com.android.egg
Bug: 251903639
Change-Id: I2ea6ed39b2e1f4877a83d0a7737537c00ce7e7a6