Add status fixtures for different state transitions

Issue: Add deployment status fixtures for different st... (#406258 - closed)

Adds realistic fixtures to ee/spec/support/shared_contexts/remote_development/remote_development_shared_contexts.rb#create_workspace_agent_info

Note that this is incomplete. The incomplete fixtures raise AgentInfoStatusFixtureNotImplementedError, which is caught in the corresponding examples in ee/spec/lib/remote_development/actual_state_calculator_spec.rb, and causes the example to be skiped and not fail.

See related docs at https://gitlab.com/gitlab-org/remote-development/gitlab-remote-development-docs/-/blob/main/doc/workspace-updates.md

Follow-up issue: Finish incomplete work on state management logi... (#407518)