[tk5] Implement slice analysis and sufficient op coverage for a softmax kernel.

[stellaraccident]

• Adds arithmetic binary broadcast.
• Adds f32 arithmetic.
• Handles torch ops exp, max, sum (only reduce to scalar at the moment).
• General python signature validation and unpacking.
• Some initial attribute propagation work needed to handle unsigned properly.
• A start at full generality for symbolic dimensions and slice analysis. Needs to be reworked before too long but this gets us basic functionality on static kernels while leaving room for dynamic to emerge.