Add autotune for matmul

[junjihashimoto]

This PR implements autotune for matmul.
To skip unacceptable parameters with runtime-exception, it also implements additional exception-hander to catch exceptions on main-thread.

[austinvhuang]

Pretty excited to incorporate some autotuning functionality in the library.

On the exception handler, I need to have a closer look. What are the condition where the exception gets thrown? Some additional discussion on errors here #49 (comment) - can chat more in the discord chat.

I was thinking about a more generic mechanism for autotuning. There could be some higher order function that takes:

1. A list of parameter sets to sweep through (a consumer of this could setup the product set of their parameters). Note the parameter set would be a value-level map (parameter name -> parameter -> value).
2. a function that takes one specific parameter set, a number N of replications per parameter set.

The autotuner then sweeps through each parameter set and runs it N times. It then returns, for each parameter set, the N values of running times. Something like hyperfine https://github.com/sharkdp/hyperfine except operating on a parameter set and a function as input.