Make benchmarks for sympy performance issues

[moorepants]

There are a number of SymPy issues with the "Performance" label. It would be helpful to make benchmarks for any issues that we do not currently have.

Issues found at:

https://github.com/sympy/sympy/issues?q=is%3Aissue+is%3Aopen+label%3APerformance