Deprecate and ignore innodb_log_checksums

The parameter innodb_log_checksums that was introduced in MariaDB 10.2.2 via MySQL 5.7.9 does not make much sense. The original motivation of introducing this parameter (initially called innodb_log_checksum_algorithm) was that the InnoDB redo log used the slow and insecure innodb algorithm. With hardware or SIMD assisted CRC-32C computation being available, there should be no reason to allow checksums to be disabled on the redo log.

The parameter innodb_encrypt_log already implies innodb_log_checksums=ON.

Let us deprecate the parameter innodb_log_checksums and always compute redo log checksums, even if innodb_log_checksums=OFF is specified.