Investigate why log.rs bug was not caught by tests

[buraksenn]

Describe the bug

While implementing https://github.com/apache/datafusion/pull/12972, I've pushed a commit with a bug for log(x,y) case. However, that CI tests were successful for that commit. Thanks to @berkaysynnada I've realized the bug and fixed it in the PR.

Tests do not cover this case or something else is wrong. I will investigate and fix the issue or extend the tests.

To Reproduce

Reverting the logic in this commit: https://github.com/apache/datafusion/pull/12972/commits/58d3d86c793a119804a1322d75eb9c3607a64df2

This should fail when log function has two arguments (base,value) since value is arg[1] in this case but it does not.

Expected behavior

slt tests or unit tests should have caught the issue.

Additional context

No response

[buraksenn]

take