Add option to not abort in diagnostic builds on data corruption

Any time WiredTiger returns a WT_PANIC error and diagnostic mode is enabled we currently abort the process - we do that to aid in debugging unexpected failures.

There are a category of issues that lead to WT_PANIC error returns which are due to an underlying data corruption - in those cases it's not helpful to abort and generate a core file, because the corruption is generally due to either an on disk failure or fallout from something that happened a long time in the past.

The reason this matters is for test cases attempting to cover data corruption cases need to behave differently when diagnostic mode is enabled if WT_PANIC triggers and abort.