perf(core): load tile sizes from tag if it is already loaded

[blacha]

Motivation

to read a tile you need both the tile offset and size of the tile, a optimization that COGs do is to store the tile size just before the offset, so that if you read a chunk of data near the offset you generally get both the tile size and the content of the tile

in some conditions this can result in multiple reads of the remote datasource, one to get the tile offset then one to get the tile content.

The tile size is also stored in the TileByteCounts tiff tag and if that is already loaded it should be the preffered method of fetching the tile size.

Modification

If the tile byte size tiff tag is loaded read the tile size from that tag instead.