Remove module `jacocoagent` from `TARGET_CORE_JARS`.

Before this change, `jacocoagent` was conditionally added to
`TARGET_CORE_JARS`. However, this module is not really part of the
Android Core Libraries (also, we plan to remove `TARGET_CORE_JARS`
from `PRODUCT_PACKAGES`). Remove it from `TARGET_CORE_JARS` while
keeping it in `PRODUCT_PACKAGES` and `PRODUCT_BOOT_JARS`, to keep
having it installed and being part of the boot class path on
devices (under the same conditions).

Test: Check that:
        export EMMA_INSTRUMENT=true
        && unset EMMA_INSTRUMENT_STATIC
        && m installclean
        && m systemimage
      generates a system image that contains these files:
        /system/framework/apex-jacocoagent.vdex
        /system/framework/boot-jacocoagent.vdex
        /system/framework/jacocoagent.jar
        /system/framework/<arch>/apex-jacocoagent.art
        /system/framework/<arch>/apex-jacocoagent.oat
        /system/framework/<arch>/apex-jacocoagent.vdex
        /system/framework/<arch>/boot-jacocoagent.art
        /system/framework/<arch>/boot-jacocoagent.oat
        /system/framework/<arch>/boot-jacocoagent.vdex
Test: Run test ATP test avd/avd_boot_health_check on build target
      cf_x86_phone-userdebug_coverage
Bug: 143304991
Bug: 142944799

Change-Id: Ib047a394342aeffbfec26ebc756159f145d6523e