chore: stop treating dirs as having size 128 (#10750)

Resp. directories for the database, and both dirs and symlinks for
`FileInfo.FileSize`. Instead handle it in the UI progress percentage. We
even already have special cases there for deletions, might as well
handle directories just like any other zero-sized needed item there.

This went through the very thorough testing of running it on my laptop,
the migration was applied and it seemed to be working fine after.

---------

Signed-off-by: Simon Frei <freisim93@gmail.com>

internal/db/sqlite/util.go

@@ -106,6 +106,10 @@ func (i indirectFI) FileInfo() (protocol.FileInfo, error) {
 		fi.Blocks = bl.Blocks
 	}
 	fi.Name = osutil.NativeFilename(fi.Name)
+	// Undo earlier behaviour of setting a synthetic size on dirs.
+	if fi.Type != protocol.FileInfoTypeFile && fi.Size > 0 {
+		fi.Size = 0
+	}
 	return protocol.FileInfoFromDB(&fi), nil
 }