Respect JIT-zygote config when generating boot image location.

Earlier CL Ida40dfae8c83bf7c2e737d5c7ea418e1197ad826 introduced
Soong-generated Make variable 'DEXPREOPT_IMAGE_LOCATIONS'. That CL was
erroneous in that it did not take JIT-zygote config into account and
generated identical location for "boot" and "apex" boot images.

This caused build breakages, because in case of JIT-zygote config the
two variables 'DexPreoptImages' and 'DexPreoptImageLocations' in the
module's dexpreopt.config were out of sync: 'DexPreoptImages' was
for the "apex" image, and 'DexPreoptImageLocations' was for the "boot"
image.

CL I9a91fc48e54d7d43abec2cb2b5a11e3581db380b introduced a workaround
for this problem: incorrect 'DexPreoptImageLocations' from the module
dexpreopt.config was ignored, and instead boot image location was
manually reconstructed from 'DexPreoptImages'. This workaround would
not work when we start using boot image extension and location will
become more complex.

This CL fixes the way 'DexPreoptImageLocations' is generated by
spliting the 'DEXPREOPT_IMAGE_LOCATIONS' variable in two variables
depending on the boot image flavour "boot" of "apex". This is
aligned with the way other similar variables are generated.

Test: aosp_walleye-userdebug boots.
Test: walleye_jitzygote-userdebug builds
  (on git_rvc-release branch with this CL cherry-picked).

Change-Id: I93415227564522bce4250d281d561e708a022101