Ability to customize Rate Limit config to tower

[obonyojimmy]

New feature

id like to customize the rate-limit config currently hardcoded in nextflow

nextflow/modules/nf-commons/src/main/nextflow/util/RateUnit.groovy

Line 78 in 73899f3

* - ie. max 100 task per 5 minutes

that would enable nextflow to send customizaable trace events to tower.currently a workflow with many process takes a while to reach tower whislt nextflow has finished processing the workflow caused by max 100 task per 5 minutes

Usage scenario

nextflow run ... -with-tower --- -rt-min <some rate value>