Sometimes we'll resolve using bare `Gem::Dependency` instances rather
than `Bundler::Dependency` instances, which is fine, simpler, and saves
some memory.

When resolving from scratch a Gemfile including only `"gem "rails", "~>
8.0.1"`, I get the following results:

### Before

Total allocated: 277.48 MB (3384318 objects)
Total retained:  117.53 MB (1338657 objects)

### After

Total allocated: 265.06 MB (3186053 objects)
Total retained:  116.98 MB (1302280 objects)

https://github.com/rubygems/rubygems/commit/c6dc2966c5