Internal: remove bwc leftover

This caused some test failures as the readFrom method was not in sync anymore with the writeTo
Internal: remove some more bwc code

Some more code that was left for backwards compatibility can now be removed on master since 2.0 will require a full cluster restart.

Closes #8778
Internal: remove optional original indices

Original indices are optional in ShardDeleteByQueryRequest only for backwards compatibility, see #7406. We can remove this in master since 2.0 will require a full cluster restart.

Closes #8777
[TEST] Fix Link permission to create symoblic links in temp dirs
[Store] Only fail recovery if files are inconsistent

the recovery diff can return file in the `different` category
since it's conservative if it can't tell if the files are the same.
Yet, the cleanup code only needs to ensure both ends of the recovery
are consistent. If we have a very old segments_N file no checksum is present
but for the delete files they might be such that the segments file passes
the consistency check but the .del file doesn't sicne it's in-fact the same
but this check was missing in the last commit.
Core: surgically removed slow scroll, because master (2.0) requires full cluster restart coming from previous versions.
[TEST] produce valid symlinks in tests