[lldb/Python] Add lldbconfig module to make the lldb module configurable

Using the approach suggested by Pavel in D77588, this patch introduces a
new lldbconfig module that lives next to the lldb module. It makes it
possible to make the lldb module configurable before importing it. More
specifically it makes it possible to delay initializing the debugger,
which is needed for testing the reproducer.

Differential revision: https://reviews.llvm.org/D77661