`SafeWriteStream` may not need to `Flush` on disposal

[peppy]

At some point I'd like to confirm whether this is required. the Flush call adds an overhead, but now that we are File.Moveing the output I'd want to know whether this overhead still exists on the Move operation, and if so, whether removing the inheritance is in our best interest (from either a simplicity or performance angle).

[smoogipoo]

The flush is intended to prevent 0-byte files. Do we have another mechanism for this somewhere?

[peppy]

I'm just curious if the Move operation will cause the flush to occur implicitly. Unsure how the windows file IO API works.