Correctly serialize class loader context for "any" SDK version to JSON.

Previously "any" was serialized as its numeric value, 10000. But other
code in makefiles and scripts expects string "any", and dexpreopt.config
files generated by Make (for Android.mk modules) have "any" not 10000.

Bug: 214255490
Test: lunch aosp_cf_x86_64_phone-userdebug && m && launch_cvd \
    && adb wait-for-device && adb root \
    && adb logcat | grep -E 'ClassLoaderContext [a-z ]+ mismatch'
    # empty output, no errors at boot
Change-Id: Id5e80eb8a90d9786b5cb999c172aaecb44952f76