Support remote files for conda directive

[ewels]

It would be great to be able to support loading remote files for the conda directive. For example, the conda lock files generated by Wave:

process FOO {
    conda 'http://wave.seqera.io/v1alpha1/builds/bd-f1b208aecc9fac93_1/condalock'

Logic would ideally be similar to that used by includeConfig, whereby https or ftp protocols are recognised, the file downloaded locally and the path replaced with the local path.

Originally raised by @pinin4fjords in #5453 - see original issue for examples of current failure / error messages. Splitting that issue into two to keep discussion focussed.