Add metacache query module

[sofstam]

PR checklist

This PR closes: #7852

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the module conventions in the contribution docs
• If necessary, include test data in your PR.
• Remove all TODO statements.
• Emit the versions.yml file.
• Follow the naming conventions.
• Follow the parameters requirements.
• Follow the input/output options guidelines.
• Add a resource label
• Use BioConda and BioContainers if possible to fulfil software requirements.
• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • For modules:
    • nf-core modules test <MODULE> --profile docker
    • nf-core modules test <MODULE> --profile singularity
    • nf-core modules test <MODULE> --profile conda
  • For subworkflows:
    • nf-core subworkflows test <SUBWORKFLOW> --profile docker
    • nf-core subworkflows test <SUBWORKFLOW> --profile singularity
    • nf-core subworkflows test <SUBWORKFLOW> --profile conda

[Gullumluvl]

How about groovy code here, instead:

def dbmeta = db.find{ f -> f.name =~ $/\.meta$$/$ }

[Gullumluvl]

Ah sorry, did not understand that input db is a directory. Doesn't it make easier to provide the list of files? Because the output of METACACHE_BUILD is (currently) not inside a directory. (Then we would have to replace UNTAR with UNTARFILES in the tests).

[Gullumluvl]

My main question is about the db input being a directory. Should I change the METACACHE_BUILD module (#8209) to emit a directory instead?

[Gullumluvl]

To be exhaustive (maybe for later), we could add the optional output generated with the option -abundances.

    path "abundances.table", emit: abundances, optional: true

Could be triggered by adding a boolean input val abundances.