Support package-defined import scope

[Yethal]

Related problem

Currently whenever we install a package we add to scope all of the exported symbols via use package.nu *. However, some packages may want to only add a portion of their exported symbols to their global scope (or even none at all).

Describe the solution you'd like

Package metadata should contain a list of symbols that should be imported into the global scope during package installation. This list should be read during package installation and used to build the import expression instead of the hardcoded use package.nu * we use currently.
Symbol list should support some sort of wildcard (* ?) to allow maintainers to export all symbols from module without listing them one by one.
Installation of packages with no exported symbols should effectively behave the same regardless of whether --add-to-scope flag was added

Describe alternatives you've considered

No response

Additional context and details

No response