LU-10026 osd-ldiskfs: use preallocation for dense writes

LU-10026 osd-ldiskfs: use preallocation for dense writes

use inode's preallocation chunks as per-inode group preallocation:
just grab the very first available blocks from the window.

Test-Parameters: env=ONLY=1000,ONLY_REPEAT=11 testlist=sanity-compr
Test-Parameters: env=ONLY=fsx,ONLY_REPEAT=11 testlist=sanity-compr
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I9d36701f569f4c6305bc46f3373bfc054fcd61a9
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50171
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>