buf_buddy_relocated_duration[],
page_zip_compress_duration[]
page_zip_decompress_duration[]: Record the total duration of the operations.

buf_buddy_relocate(), page_zip_compress(), page_zip_decompress():
Add ut_time_us() instrumentation.

i_s_zip_fields_info[], i_s_zip_fill_low(): Move the columns containing
cumulated statistics last.  Add relocated_usec, compressed_usec, and
decompressed_usec.