Improve ignore specification to allow negation of specific directories

[prototaxites]

Currently in the nf-test.config for the nf-core template, we have:

ignore = [
        'modules/nf-core/**/tests/*',
        'subworkflows/nf-core/**/tests/*',
    ]

This excludes tests coming from the nf-core modules repo from running during testing.

Using nf-core tools, it is possible to also install modules from other repositories which may have their own tests, for example ours, sanger-tol. You can exclude these tests by adding explicit extra entries, but this requires a separate entry for each repository as Java globs don't seem to support negation.

It would be good to extend this syntax in some way so we can do something like the following, excluding all tests except those matching the "local" directory, allowing a more simple expression:

ignore = [
        'modules/!{local}/**/tests/*',
        'subworkflows/!{local}/**/tests/*',
    ]