Use nf-test for input validation

[drpatelh]

Description of feature

Tried to switch to using nf-validation for the input id validation but hit this issue https://github.com/nextflow-io/nf-schema/issues/10

Created this issue as a tracker. Changes required after the fix can be seen in this commit https://github.com/nf-core/fetchngs/pull/252/commits/d2fac84715db4b925e54a6cfdda4360d057459c8