fdo#76140: Reimplement XIRR OpenCL test.

1) Use ods format and store the expected formula results as numeric cells,
   to avoid having to load the same file twice (which is slower).

2) Use rtl::math::approxEqual to evaluate two numbers that may be subject
   to numerical instability especially when the expected values are very
   small.

Change-Id: Ie08e91f797065f4593f996df3541da84019cc53c