Add support for specifying CPU for Snakemake head job

[KevinSayers]

Description

The Snakemake head job currently runs on Fargate with 1 vcpu. It would be useful to be able to specify additional resources for the head job. In particular, when Snakemake creates the Conda environment it can be quite slow with limited resources.

Use Case

Execution of workflows that require the head job to utilize additional resources such as with Conda environments.

Proposed Solution

Provide a way to specify the resource requirements.

contexts:
  onDemandCtx: 
    headJobCPU: 4 #Or something along these lines. 
    engines:
      - type: snakemake
        engine: snakemake

Other information

[johnnephin]

Any update on this feature? Are there any workarounds until this is implemented?