[lldb/Reproducers] Capture reproducers from the API test suite.

Make it possible to capture reproducers from the API test suite. Given
the symmetry between capture and replay, this patch also adds the
necessary code for replay. For now this is a NO-OP until the
corresponding reproducer instrumentation changes land.

For more info please refer to the RFC on lldb-dev:
http://lists.llvm.org/pipermail/lldb-dev/2020-April/016100.html

Differential revision: https://reviews.llvm.org/D77588