Deprecate the support for Mamba/Micromamba

[pditommaso]

Nextflow provides built-in support for Conda package manager to setup the task environment.

However, Conda can be considerably slow in resolving the package dependencies, for this reason alternative tools such as mamba and micromamba have been emerged to provide a faster resolution.

Nextflow supports also those tools, however this adds extra complexity in the underlying implementation.

Considering that now Conda does support the use of libmamba directly for the package resolution, this ticker aims to deprecate the direct support for Mamba and Micromamba in Nextflow considering this capability can be enabled by the user in the Conda toolset.

See here for more details https://www.anaconda.com/blog/a-faster-conda-for-a-growing-community