HPCC-33526: Update datamaskingtests failure identification and reporting

Use framework assertion macros to identify and report failures.
- Do not throw exceptions to signal failure.
- Do not report failures using [f]printf.
- Improve accuracy of failure reporting.
- Eliminate overhead associated with manual failure logging.

Signed-off-by: Tim Klemm <Tim.Klemm@lexisnexisrisk.com>

Author: Tim Klemm