[lldb] Add reproducer verifier

[lldb] Add reproducer verifier

Add a reproducer verifier that catches:

 - Missing or invalid home directory
 - Missing or invalid working directory
 - Missing or invalid module/symbol paths
 - Missing files from the VFS

The verifier is enabled by default during replay, but can be skipped by
passing --reproducer-no-verify.

Differential revision: https://reviews.llvm.org/D86497