BoundingBox inaccuracy

Description

pc.BoundingBox stores two vectors: center and halfExtents. The minimum and maximum values can be calculated from these values using getMin and getMax. The problem with this is rounding errors. The currently only way to get the actual minimum and maximum is to loop over the vertexbuffer and calculate them manually.

To fix this problem pc.BoundingBox has to be remade to store the minimum and maximum values and calculate center and halfextents from them.

Steps to Reproduce

Run this code in any project.

let min = new pc.Vec3(0.3,1,1);
let max = new pc.Vec3(2.7,1,1);
let aabb = new pc.BoundingBox();
aabb.setMinMax(min, max);
console.log(aabb.getMin().x);
// output: 0.2999999999999998
console.log(aabb.getMin().x === min.x);
// output: false

Start by locating pc.BoundingBox and its setMinMax, getMin, and getMax methods, then inspect how center and halfExtents are used elsewhere. Add coverage for the provided min/max example and verify that the reported bounds match the original vectors without rounding changes.