Fix ULP bound for MAX_RESIZE mode

This now correctly computes the ULP bound relative to the maximum
absolute input, while previously we were computing it relative to the
reference output.

Extend the unit test coverage for max resize verification to catch
regressions and other bugs in bfloat16 and float16

Refactor a calcAbsErrorBound function matching the spec to use across
verification code.

Signed-off-by: Ian Tayler Lessa <ian.taylerlessa@arm.com>
Change-Id: I04b08d5d160258c560dbfde3b70247d76bf3f225