Add tests for baseTypeLowest/Max/Smallest/Epsilon

Various class templates declare methods that return lowest/max/smallest/epsilon on the template base type, e.g.
```
V2f::baseTypeLowest()
V2f::baseTypeMax()
V2f::baseTypeSmallest()
V2f::baseTypeEpsilon()
```

These methods are not covered in the test suite. Entries should be added to the python test [src/python/PyImathTest/pyImathTest.in](https://github.com/AcademySoftwareFoundation/Imath/blob/main/src/python/PyImathTest/pyImathTest.in)

Open src/python/PyImathTest/pyImathTest.in and review the existing entries for related class-template methods. Add coverage for baseTypeLowest, baseTypeMax, baseTypeSmallest, and baseTypeEpsilon on the named examples, then run the Python test suite. Done means these methods are exercised by the test suite.

Written by the indexing model from the issue text.