Fix plugin installation from gemfile

[ccutrer]

What was the end-user or developer problem that led to this PR?

This fixes #6630 and several related issues. Related to #6643, but a very different approach. Specs were copied from that PR though.

What is your fix for the problem, implemented in this PR?

Instead of blindly calling the installer with the plugins from the gemfile, build a virtual lockfile from the plugin index. Then only call the installer if it needs to be resolved. This fixes several issues:

• Avoids re-installing a plugin every time bundle install is called
• Avoids even reaching out to get gem metadata if the plugin is already satisfied (not solved by [Plugin] Fix "Installing" bug when install plugin from Gemfile #6643, and would be very difficult to solve with the after-resolution approach to skipping unnecessary installs)
• If the plugin referenced in the index doesn't satisfy the version constraint, it will be reinstalled ([Plugin] Fix "Installing" bug when install plugin from Gemfile #6643 has a bug here when used with path based plugins, though it would be easy to solve in the same manner that I extract the version in this PR)

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

[ccutrer]

I've confirmed this also fixes #6589

[pboling]

This is awesome 🎸

[slaughter550]

@pboling anything else you wanted to see on this PR?

[pboling]

Moving the ball forward on plugins is amazing. There is probably still some gap before I can do what I was hoping with plugins, but this is a great step toward making them more of a first-class citizen within bundler.

[deivid-rodriguez]

This is indeed pretty cool! @ccutrer can you rebase this?

[ccutrer]

There are several conflicts. I'll try to get them resolved later today.

[ccutrer]

Rebased and conflicts resolved; I didn't run rubocop or specs locally -- I'll let GitHub Actions handle that

[deivid-rodriguez]

@ccutrer I assume test failures here mean this still needs some work? Happy to have a look if needed!

[deivid-rodriguez]

Adding a review comment here so we don't forget when we work on this PR: we should add @dfop02 attribution to the commit adding these specs, since he is the original author.

[ccutrer]

Yes, this still needs attention. I'm sorry I haven't had time for it - have had other priorities at work.

[deivid-rodriguez]

No problem at all!