[Part 2] 5276 Update existing stores for terminal file sync

What does this MR do?

CE Port => https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29333

This MR is part of the larger WIP MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/12239.

This MR updates the existing stores to support the terminal file sync.

• Adds triggerFilesChange action to main IDE store.
• Adds relevant dispatches to this action.
• Adds some properties which have been added in the BE to the terminal session response action.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Closes #5276 (closed)