Switch to typetracer

[mpadge]

Instead of the miles of code currently used to parse example code and identify input types

[mpadge]

https://github.com/mpadge/typetracer is now all set to implement here.

[mpadge]

The above commits are hopefully heading towards most of the work. One issue that has arisen is that many more tests are generally run, and these include code from test suites which is designed to trigger errors. Current typetracer output still can not identify the ultimate source of traces, so has no way of ascertaining whether a trace might represent a call that is actually intended to fail. This results in spurious error messages. I think the only safe way to solve this will be to modify typetracer to enable identificaiton of the calling environment. At least for "testthat", this should be possible, and so traces from within a testing environment can be used for determining parameter types, while all of the actual mutation and autotesting can be based on example code alone.