Support adding layers and context to container build

[munishchouhan]

This PR will do the following:

1. Fix posix permission issue in singulairty build when untar layers
2. Fix posix permission issue when untar context

[pditommaso]

I think this can be simplified without handling in a special case the saving of build context and layers for singularity

wave/src/main/groovy/io/seqera/wave/service/builder/impl/ContainerBuildServiceImpl.groovy

Lines 272 to 279 in 3471824

	if(req.formatDocker()) {
	saveLayersToDockerContext0(req, contextDir)
	}
	else if(req.formatSingularity()) {
	saveLayersToSingularityContext0(req, contextDir)
	}
	else
	throw new IllegalArgumentException("Unknown container format: $req.format")

In both cases, Wave should only take case of saving the tar in the build work dir (s3 path). then mounting that path in the content. Finally Dockerfile add it/them to the container using one or more ADD, instead singularity using a %post script to untar and copy in the right directory

[munishchouhan]

Tested singularity in dev:
https://wave.dev-seqera.io/view/builds/bd-f3d0dbf41f09b917_1

[munishchouhan]

tested docker with context
https://wave.dev-seqera.io/view/containers/5f81208b7fae

[munishchouhan]

tested singulairty with context
https://wave.dev-seqera.io/view/builds/bd-553d7de13471d357_1