Add bundler ecosystem extension

[cd-work]

Closes #1178.

[kylewillmon]

Might need some testing (which I believe @maxrake is currently doing), but the code looks good now.

[maxrake]

Local testing was performed with some limitations. The Phylum processing pipeline was delayed beyond the 30 minutes advertised and therefore it was not possible to see the full results of some phylum bundle add commands. More local testing will be performed after the requested changes are addressed.

It would also be nice if this extension included tests, like how the poetry extension does.

[maxrake]

Local testing was performed and the extension worked as expected for the install, add, and update commands.

There is still a question about the remove command, which is not covered but does install gems. The README says:

When invoking phylum bundle, subcommands that would install gems will trigger a Phylum analysis first.

Adding the remove command for coverage or creating a new issue for it and any other affected ecosystem extensions is requested.

It would also be nice if this extension included tests, like how the Poetry extension does.

[cd-work]

There is still a question about the remove command, which is not covered but does install gems.

This wouldn't be difficult, but should be made a consistent policy if we want to enforce it. Bundle also has an option to not install packages on remove for example.

It would also be nice if this extension included tests, like how the Poetry extension does.

The poetry extension tests have never provided anything but trouble to me. I didn't write them and I wasn't ever a fan of them. So I have no intention of adding more for this extension.

[maxrake]

The latest changes were confirmed with local testing. LGTM.