[feature] Use of moduleTestDir instead of projectDir in nf-test for genomics when referring to test data

[adamrtalbot]

In nf-test for genomics, the test data path is referred from the projectDir:

    test("Should call trio's joint genotype correctly") {

        when {
            params {
                outdir = "tests/results"
            }
            process {
                """
                input[0] = [
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_father.bam.g.vcf"),
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_mother.bam.g.vcf"),
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_son.bam.g.vcf")
                ]
                input[1] = [
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_father.bam.g.vcf.idx"),
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_mother.bam.g.vcf.idx"),
                    file("${projectDir}/modules/gatk/jointgenotyping/tests/inputs/reads_son.bam.g.vcf.idx")
                ]
                input[2] = file("${projectDir}/data/ref/intervals.bed")
                input[3] = "family_trio"
                input[4] = file("${projectDir}/data/ref/ref.fasta")
                input[5] = file("${projectDir}/data/ref/ref.fasta.fai")
                input[6] = file("${projectDir}/data/ref/ref.dict")
                """
            }
        }

However this is pretty verbose and we could replace it with the moduleTestDir from the nf-test global variables:

    test("Should call trio's joint genotype correctly") {

        when {
            params {
                outdir = "tests/results"
            }
        process {
            """
            input[0] = [
                file("${moduleTestDir}/inputs/reads_father.bam.g.vcf"),
                file("${moduleTestDir}/inputs/reads_mother.bam.g.vcf"),
                file("${moduleTestDir}/inputs/reads_son.bam.g.vcf")
            ]
            input[1] = [
                file("${moduleTestDir}/inputs/reads_father.bam.g.vcf.idx"),
                file("${moduleTestDir}/inputs/reads_mother.bam.g.vcf.idx"),
                file("${moduleTestDir}/inputs/reads_son.bam.g.vcf.idx")
            ]
            // I haven't replaced these but these could be included:
            input[2] = file("${projectDir}/data/ref/intervals.bed")
            input[3] = "family_trio"
            input[4] = file("${projectDir}/data/ref/ref.fasta")
            input[5] = file("${projectDir}/data/ref/ref.fasta.fai")
            input[6] = file("${projectDir}/data/ref/ref.dict")
            """
        }
    }

This could reinforce the idea of a "module dir" including tests and data.