integrity: add --integritysettings for tuning

integrity: add --integritysettings for tuning

The option can be used in multiple ways (like --cachesettings):

--integritysettings key=val
--integritysettings 'key1=val1 key2=val2'
--integritysettings key1=val1 --integritysettings key2=val2

Use with lvcreate or lvconvert when integrity is first enabled
to configure:
journal_sectors
journal_watermark
commit_time
bitmap_flush_interval
allow_discards

Use with lvchange to configure (only while inactive):
journal_watermark
commit_time
bitmap_flush_interval
allow_discards

lvchange --integritysettings "" clears any previously configured
settings, so dm-integrity will use its own defaults.

lvs -a -o integritysettings displays configured settings.