Warnings and assertions defined as `config.warnings` and `config.assertions`
respectively will be checked as part of the test derivation, instead of
when evaluating the modules.
Adds new `checkWarnings` and `checkAssertions` test options (default true).
Introduces the `test.runNvim` module option.
Deprecates the historic `dontRun` argument passed to the test-derivation
helpers.
Soft-deprecates the `tests.dontRun` attr used in tests currently.