Add support for Tugboat MR previews to create D10 and 11 previews

Problem/Motivation

Tugboat previews on merge requests are a huge help to module maintainers and contributors. The Tugboat config.yml can support the creation of multiple servers for example a Drupal 10 preview and a Drupal 11 preview in the same Tugboat instance (might not be the right word). My understanding is that it is really just the UI within the issue that does not currently support showing links to the two variations.

Steps to reproduce

1. Go to an issue
2. Create a merge request for the issue
3. Observe that only one link is created for the preview.

Proposed resolution

If the .tugboat/config.yml creates two different php servers, then links should be provided to both.

Remaining tasks

1. Make the links in the UI surface multiple servers - this however could be disregarded if the UI had a link to access the Tugboat Dashboard, which would already show links to each environment.
2. Add an example to the documentation to show how to create a D10 and D11 versions

User interface changes

API changes

Data model changes