This commit honors the compiler version requirement listed in the solc
modes of the metadata file. If this version requirement is provided then
it overrides what was passed in the CLI. Otherwise, the CLI version will
be used.
This commit updates how logging is done in the differential testing
harness to use `tracing` instead of using the `log` crate. This allows
us to be able to better associate logs with the cases being executed
which makes it easier to debug and understand what the harness is doing.
Omar Abdulla