[VSCode] Add terminal_context status check

Problem to solve

In &17312 we will add a new "Explain terminal output" command to VSCode, which will trigger a Duo Chat message containing selected terminal output as attached context.

This will be associated with the new include_terminal_context unit primitive: gitlab-org/cloud-connector/gitlab-cloud-connector!107 (merged)

Unlike the other chat related unit primitives, this new context will not be added directly via the Duo Chat UI, and instead will be provided from a VSCode context menu (right clicking inside the VSCode terminal when there is a selection). As such, the existing unit primitive status checks won't automatically apply to this case.

The language server will expose a new status check: gitlab-org/editor-extensions/gitlab-lsp#931 (closed)

Proposed solution

Integrate the new status check in VSCode