Port bedtools_genomecov from local to nf-core module

[FloWuenne]

Description of feature

Description

Currently, the bedtools_genomecov module is implemented as a local module. There is however an nf-core module for it https://nf-co.re/modules/bedtools_genomecov. The local module should probably be ported to the nf-core module to ensure maintenance and allow users to set parameter space using ext.args, instead of relying on hard coded parameters for every execution, for example --bg / --bga (as described in https://github.com/nf-core/chipseq/issues/468)