COG reader should have an adaptive strategy to read large headers

[aaime]

The default read size (16kb?) works for small COG files, but large ones with a massive amount of tiles need too many reads in order to fully load the header. Maybe the reader should have an adaptive strategy starting small and growing the size of the read (up to a given maximum) to quickly read large headers. I don't know, something like doubling the page size of the read at each attempt, until a maximum of N megabytes is reached.

[samodadela]

@aaime About the header. Is it cached? What if the layer is tiled - will each tile request load the header again?

[aaime]

It's cached. Fully. That's the issue with large headers, they sit in memory all the time.