Move explain_terminal unit primitive to included context

What does this MR do and why?

Migrates the explain_terminal unit primitive to include_terminal_context.

Context - explain_terminal was never implemented in the AI Gateway / Rails Monolith. Since that unit primitive was originally added, the direction has changed to utilize the "injected context" feature instead. To accomplish this, we must rename the primitive.

See Implement command for explaining terminal outpu... (gitlab-org/gitlab#504104 - closed) for details.

Merge Chain ⛓️

Project	MR	-
Cloud Connector	Move explain_terminal unit primitive to included context	<-- You are here
AI Gateway	feat: add additional context type 'terminal'
Rails Monolith	Add additional context type for terminal to API

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• Implement command for explaining terminal outpu... (gitlab-org/gitlab#504104 - closed)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

New Version Checklist

Compare link: https://gitlab.com/gitlab-org/cloud-connector/gitlab-cloud-connector/-/compare/main...tr%2Fmigrate-terminal-to-included-context?from_project_id=58733651

• If changes were made in /config or src/ruby folder
  • Change the VERSION constant to a minor version in src/ruby/lib/gitlab/cloud_connector/version.rb (according to SemVer):
    • bump a major version if the change is breaking the compatibility (changing the interface, removing Unit Primitives that are used by the backends, etc). Make sure all backends that use the library are prepared for the update.
    • bump a minor version if the change is compatible but adding a new feature (Unit Primitives added, the interface is expanded with an optional argument, etc)
    • bump a patch version if it's a bugfix, adding docs, tests, or a similar change that it is safe to auto-apply by the backends who use the library.
  • Run bundle lock in src/ruby and commit the change to Gemfile.lock.
• If changes were made in /config or src/python folder
  • Change the version: in src/python/pyproject.toml file (according to SemVer).
    • bump a major version if the change is breaking the compatibility (changing the interface, removing Unit Primitives that are used by the backends, etc). Make sure all backends that use the library are prepared for the update.
    • bump a minor version if the change is compatible but adding a new feature (Unit Primitives added, the interface is expanded with an optional argument, etc)
    • bump a patch version if it's a bugfix, adding docs, tests, or a similar change that it is safe to auto-apply by the backends who use the library.
  • Run poetry lock --no-update --verbose --no-cache and commit the change to poetry.lock
• Ensure the diff link above is up-to-date.
• Create an MR on depending Gitlab projects to bump the version.