No capex by default if RELEASE_APEX_MOUNT_BEFORE_DATA

The new feature (RELEASE_APEX_MOUNT_BEFORE_DATA) requires that there's
no compressed APEXes installed. The default value for
PRODUCT_COMPRESSED_APEX is set to false when the flag is on.

Bug: 381173074
Flag: RELEASE_APEX_MOUNT_BEFORE_DATA
Test: lunch aosp_cf_x86_64_phone-trunk_staging-userdebug
Test: m && cvd create
Test: adb shell ls /system/apex (no compressed apexes)
Change-Id: I7c53a52108205d049f747adf4c64c6d74fde03d9