LU-10496 ofd: move FMD to the target code

LU-10496 ofd: move FMD to the target code

- make FMD structures common for all targets
- adapt FMD functionality to be isolated from OFD for
  further move to the target code.

Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I9f67f14e4132205cca67aa778b990bb3b45c30be
Reviewed-on: https://review.whamcloud.com/34176
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>