Use ro.build.fingerprint instead of ro.bootimage.*

ro.bootimage.* sysprops will be removed as they are redundant. Read
ro.build.fingerprint instead.

This is safe because:
2) ro.bootimage.build.fingerprint is the same as other
ro.<partition>.build.fingerprint all of which are from
$(BUILD_FINGERPRINT_FILE).
3) BUILD_FINGERPRINT_FILE is composed of PRODUCT_BRAND, TARGET_PRODUCT,
TARGET_DEVICE, etc.
4) ro.build.fingerprint is auto-composed by init at runtime by the same
rule as #3.

Bug: 117892318
Test: enter into the recovery mode and manually inspect the title line
Change-Id: If28d710f45b98a0effc0159851bca6afb2aa5735