[jvm] sys.io.File.read is a huge performance trap

[Simn]

import haxe.io.Input;
import haxe.io.BytesInput;

function main() {
	var input:Input = sys.io.File.read("eval.zip");
	// input = new BytesInput(input.readAll()); // that line
	try {
		var zip = haxe.zip.Reader.readZip(input);
		trace("Read");
	} catch (e:Dynamic) {
		trace(e);
	}
	input.close();
}

target	without that line	with
JVM	8.101	0.637
Eval	7.781	8.454
HL	2.463	1.952
C++	5.486	2.879

[Simn]

I don't know if this is how real Java devs handle this, but it's faster for me.

[Simn]

I reverted that change because the interaction between the buffer and the random access doesn't work the way I thought it would, which breaks all tell() offsets.

Surely there must be a straightforward fix for this...