Fix inconsistent behavior of scalar Jacobi between reference and the others

[yhmtsai]

We have the workaround for zero diagonal value in scalar Jacobi, but reference uses 1 but the others uses zero. I currently make it be 1. Note. it is not the proper inverse Jacobi matrix.

first commit adds the test and the second one fixes the issue.

[upsj]

@yhmtsai the second commit seems to be missing

[yhmtsai]

@upsj Yes and sorry. I would like to wait for that some jobs of the first commit fail first

[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.60%. Comparing base (b9a8c6a) to head (7cf1b31). Report is 1 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #1642 +/- ## ======================================== Coverage 91.60% 91.60% ======================================== Files 761 761 Lines 61181 61199 +18 ======================================== + Hits 56045 56064 +19 + Misses 5136 5135 -1 ```

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