[processing] provide non-random default ordering of parameters in models

Fixes #11702
[processing] fixed handling of tables in models

Fixes #11694
[processing]removed unused code
[processing] fixed fields calculator algorithm

It's not a complete fix, as it just comments out a line that was causing a 'underlying C/C++ object was deleted' error
Should revisit is later. For now, this allows the algorithm to run correctly and not crash qgis
[processing] better behaviour for fields calculator custom dialog