[FEATURE] use `arity` in freebayes module to allow more than two input files

Is your feature request related to a problem? Please describe

BAM input handling in the current nf-code/freebayes module allows for specification of 1 or 2 bam input files (using input_1, input_1_index, input_2 and input_2_index path inputs).

However, this is not a limitation of freebayes, and furthermore nextflow allows path inputs to contain an arbitrary number of individual paths.

Describe the solution you'd like

• specify alignment and alignment_index as path inputs with arity 1..*
• provide these inputs to freebayes

Describe alternatives you've considered

No response

Additional context

No response

Locate the nf-code/freebayes module and inspect how input_1, input_1_index, input_2, and input_2_index are currently declared and passed to freebayes. Replace that interface with alignment and alignment_index path inputs using the requested arity, then verify that one or more BAM inputs can be provided successfully.