Add unit tests for function SUM and operator ^

[sequba]

Context

Unit tests written when analyzing the behavior of function SUM and operator ^.

How did you test your changes?

unit tests pass

Types of changes

• Breaking change (a fix or a feature because of which an existing functionality doesn't work as expected anymore)
• New feature or improvement (a non-breaking change that adds functionality)
• Bug fix (a non-breaking change that fixes an issue)
• Additional language file, or a change to an existing language file (translations)
• New unit tests

Checklist:

• I have reviewed the guidelines about Contributing to HyperFormula and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement.
• My change is compliant with the OpenDocument standard.
• My change is compatible with Microsoft Excel.
• My change is compatible with Google Sheets.
• I described my changes in the CHANGELOG.md file.
• My changes require a documentation update.
• My changes require a migration guide.

[github-actions]

Performance comparison of head (dcc9be8) vs base (b18f616)

                                     testName |   base |   head | change
------------------------------------------------------------------------
                                      Sheet A | 553.17 | 545.09 | -1.46%
                                      Sheet B |  186.6 | 180.82 | -3.10%
                                      Sheet T |    162 | 160.61 | -0.86%
                                Column ranges | 567.76 | 560.84 | -1.22%
Sheet A:  change value, add/remove row/column |   15.9 |  15.32 | -3.65%
 Sheet B: change value, add/remove row/column | 133.24 |  137.5 | +3.20%
                   Column ranges - add column | 166.19 | 157.82 | -5.04%
                Column ranges - without batch | 489.06 | 458.12 | -6.33%
                        Column ranges - batch | 127.15 | 118.09 | -7.13%