Migrate to nf-core-utils plugin

[edmundmiller]

Some criteria we came up with to migrate:

• Merge into 2 pipelines
  • Proposal: nf-core-utils fetchngs#348
  • rnaseq/nascent/sarek?
• Release 1.0.0 before it's added to the template
• Approval of New RFC: Migrate Subworkflows and Template boilerplate to nf-core-utils plugin proposals#51

Initially, this shouldn't add or remove any functionality. It should just be a one-to-one replacement.(I'm not going to bend over backwards to keep old functionality we don't need anymore, though.).