Add word-by-word comparison with tolerance and threshold to file diff.

[danielmayer]

Proposed Changes

The current file comparison that is used for regression tests, does not feature a possibility to specify a tolerance or a threshold. This PR implements such a feature and does not affect the existing regression tests.

Related Work

Currently, there are no regression tests that make use of this feature and the PR does not include a new test that would use it. However, the feature_new_flamelet branch already uses this feature. This branch here is to split off the feature as it is not related to flamelet models but it is a general feature that can used for a variety of regression tests that use a file comparison.

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• [O] I have added a test case that demonstrates my contribution, if necessary.
• [O] I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary.

[pcarruscag]

Thank you Daniel, LGTM after taking care of any CodeQL warnings

[bigfooted]

Thanks, Daniel, looks good.