Datafile::find_space_id(): Fix a regression that was introduced
in c0f47a4a for MDEV-12026.
Because the function buf_page_is_corrupted() now determines
the physical page size from the fsp_flags, our buffer size must
agree with the fsp_flags.

buf_page_is_corrupted(): Use the correct accessor
fil_space_t::zip_size() for convering the tablespace flags.
ROW_FORMAT=COMPRESSED files never use innodb_checksum_algorithm=full_crc32.