Feature request: Allow use of arbitrary network filesystems with the AWS batch executor

New feature

Currently, executor 'awsbatch' requires the use of a bucketDir / -bucket-dir. It looks like there's built-in support for Fusion, and a licenseable extenstion for FSx-for-Lustre and AWS EFS. It would be nice to be able to use any network filesystem with AWS batch (perhaps with less-rich support in the open-source version of nextflow).

Use case

We have a network filesystem that's none of the above (FlexFS) that's mounted in our AWS batch templates, and would like to use it with the nextflow awsbatch executor.

Suggested implementation

Add a setting for the awsbatch executor to skip the check that a -bucket-dir / bucketDir is defined, and in that case simply copy/link/etc. files into the standard workDir to stage them (assuming the workDir is on some kind of network filesystem).

Start by tracing the awsbatch executor's bucketDir validation and its work-file staging path. Compare the mentioned Fusion and FSx-for-Lustre/AWS EFS support, then define how an optional no-bucket-dir mode should stage files on a network filesystem; done means AWS Batch can use the configured workDir without requiring bucketDir.