Sort PRODUCT_UPDATABLE_BOOT_JARS.

At runtime it is now responsibility of derive_classpath to define value
of BOOTCLASSPATH. As we are modularizing BCP configs, the end goal is to
have a following ordering:

- ART APEX jars
- /system jars
- /system_ext jars
- /apex jars from non-updatable apexes
- /apex jars from updatable apexes

Note that /apex configs are sorted alphabetically, however they preserve
relative ordering of the jars exported from individual apexes. For
example, core-oj.jar would come before bouncycastle.jar if ART apex
defines their relative order as such.

To match end goal expectations of the APEX ordering, sort existing list
of PRODUCT_UPDATABLE_BOOT_JARS.

Bug: 180105615
Test: presubmit
Change-Id: I15512c0da79ad94b547325d563dac473c006f9fd
Merged-In: I15512c0da79ad94b547325d563dac473c006f9fd