Expose libminui related variables as vendor default properties.

TARGET_RECOVERY_DEFAULT_ROTATION, TARGET_RECOVERY_OVERSCAN_PERCENT and
TARGET_RECOVERY_PIXEL_FORMAT are vendor-specific properties used by
libminui. So they are needed by both of recovery and charger modes.

We used to pass them to libminui as build-time flags (pre-Q), and
switched them to runtime properties recently (available to recovery
only). Since /sbin/charger lives on system image, the values should be
still passed as runtime properties, but need to be additionally
available under charger mode, and overridable by vendor-init.

This CL writes these variables as vendor default properties (i.e.
/vendor/default.prop if property_overrides_split_enabled is true,
otherwise into /default.prop). Note that writing them as vendor build
properties doesn't work, as init doesn't load /vendor/build.prop under
charger mode.

Bug: 113567255
Test: Build along with other CLs in the topic (for sepolicy and
      libminui changes). Boot into charger mode.
Test: Boot into recovery. Run graphics test.
Change-Id: Iccc4de0fbff508d489fc93b45c2ecfd0fb96053c