Unlock related Gemfile dependencies, but not everything that changed

[deivid-rodriguez]

#7621 fixed an issue where some dependencies were not getting requirement updates in the Gemfile in situations where users would usually expect them.

However, the fix was too aggressive and it caused also unrelated dependencies to the update being unlocked under some situations.

This PR implements a hopefully safer approach.

Fixes #8195.

[jakecoffman]

There are a number of grouped updates issues in the Bundler ecosystem this may fix as well.

[Nishnha]

This makes sense to me!

[deivid-rodriguez]

During testing I found that this approach was creating several PRs for the same dependency sometimes (auto-grouped with others, and single dependency PRs). I changed the approach to one that's simpler and does not have this issue, namely, if any other top level dependencies changed versions during "force update", then add those too to the updated_dependencies array.