blob: fix races between iterator instances

This fixes crashes in case of multiple iterators used, because
previously any subsequent iterator could remap bctl->data used by
another iterator.
blob: check that bctl->data is still valid on iteration
blob: do not disable defragmentation while iterating

Now that we have proper locking on iteration path it should be safe.
blob: eblob_write_ll already zeroes out wc
blob: remove useless assignment
blob: renamed blob_update_index() to eblob_update_index()
blob: fixed fallthrough comment position
blob: create eblob_wc_to_dc() subroutine
blob: rename blob_write_prepare_ll() to eblob_write_prepare_ll()
blob: code cleanup
blob: formatting in eblob_check_disk_one()
ci: increase default test iterations, but remove logging
blob: spacing in eblob_check_disk_one()
mobjects: clarify libc error code checks
mobjects: spacing and comments
defrag: removed old defrag code for good

Also added msync call after index is sorted to protect against power
loss.
blob: added thread for various periodic tasks
index: removed now unused eblob_find_exact_callback
mobjects: simplified eblob_iterate()
blob: do not depend eblob_check_free_space on stats' fd