ecs

Implement entity physics: gravity and collisions with blocks.

The basic algorithm for Minecraft entity physics is, each tick, to:

1. Add velocity to position.
2. For each axis (X/Y/Z) individually, check for collisions between the entity's bounding box and blocks. If there are any, clamp the entity's position to the edge of the block. There are some useful details on collision detection [here

While testing another PR, I found that mu pipeline logs command displays information from the pipelines, but also shows this error:

$ mu pipeline logs
[... normal, expected output ...]
func1 ▶ ERROR  ResourceNotFoundException: The specified log group does not exist.
	status code: 400, request id: f7260741-7f69-4772-b4cc-7c6a9c22d264

This error does not occur with the `-f