Metapackages should register their sub-packages as explicitly installed

[wspear]

Summary

When a metapackage such as ecp-data-vis-sdk installs requested 'sub-packages' those packages are treated as typical dependents and not flagged as explicit installs.

Rationale

Metapackages essentially hide the packages they provide from any logic operating on explicitly installed packages. This is an issue for E4S in particular since we generate reports and run tests on explicitly installed packages. This is potentially an issue for general users who may want to locate a metapackage-provided package for their direct use and will have to jump through additional hoops to distinguish it from other installs of the same package that were implicitly installed as dependencies of other packages.

Description

I suggest adding an API feature to manually tag a dependency as explicit from within a spack package. When this is available (or if it already exists) I suggest applying it to the packages installed by ecp-data-vis-sdk and similar metapackages.

Additional information

Observed as of: 0.19.0.dev0 (42de3ff968f8bc32221ced071ba3633bca670bb4)

@eugeneswalker @kwryankrattiger @tgamblin

General information

• [X] I have run spack --version and reported the version of Spack
• [X] I have searched the issues of this repo and believe this is not a duplicate