fix: don't print the funding message for global installs (#9864)

## What / Why

A global install prints "N packages are looking for funding / run `npm
fund` for details", but nothing can be done with it. `npm fund -g` fails
with `EFUNDGLOBAL`, and a bare `npm fund` loads the tree at the local
prefix, so outside a project it prints the directory name and nothing
else.

`packagesFundingMessage` in `lib/utils/reify-output.js` never looked at
`npm.global`, so the hint went out for global installs too. It now
returns early in that case. Making `npm fund -g` work is a separate
feature request; #3112 already splits it out that way.

## Testing

New case in `test/lib/utils/reify-output.js`, mirroring the existing
`fund: false` one: with `global: true` the output no longer mentions
funding. It fails without the change.

## References

Fixes #9863
Fixes #3112