Add tests for RecordIterator that start at interior position.
Add tests for getIteratorForRepair().
Add tests for getManyIterators().
Add tests for truncate().
Add tests for touch().
Start on validate() tests.

The ValidateAdaptor is only used by the implementation when both
`full` and `scanData` are true.
Refactor validate() tests to use fixture.
Add more validate() tests.

Test all combinations of full=true/false and scanData=true/false.
Add tests for setCustomOption().

Includes a small fix for the heap1 storage engine since
ErrorCodes::InvalidOptions should be returned for a unsupported
option instead of ErrorCodes::BadValue.