TestConfig should have option `delete`

[rschwarz]

Not all implementations of Optimizer support deletion of variables or constraints. However, MOI.delete is used often in the tests, e.g. in linear1test.

Note that there is already the option TestConfig.modify_lhs but deletion is not guarded in a similar fashion.

[joaquimg]

1, 5, 7 and 14 are the linear ones that use MOI.delete, you can disable this ones. If you feel some feature of these tests are missing in the other ones you can propose a new one (always appreciated), we are encouraging people to create simpler and more atomic tests.

[rschwarz]

Yes, I also excluded 11.
The idea of the test config option came up on Gitter, since from my newcomer's point of view, it looked like the first test was the most fundamental (# Basic solver, query, resolve).

[joaquimg]

I agree, the names are bad in that sense. We could add a session in the manual with suggestions about how to implement solver tests.

[odow]

Closed by #1408