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
(cherry picked from commit ca25cdcb398f200ce5d53286eea02d49d8d1c5f4)
Signed-off-by: Michael Meeks <michael.meeks@collabora.com>