Create terminal smoke test suite

[Tyriar]

The terminal used to have 1-2 simple smoke tests which just echoed text and checked it. We should look into creating more involved smoke tests and potentially exposing TerminalService to the smoke tests if that would make testing easier.

Problem areas we should look at covering:

• Perfect layout size (terminal-layout.test.ts)
  • Cells aren't cut off
  • Perfect scroll bar positioning
  • Toggle size to content width
• Profiles (terminal-profiles.test.ts)
  • New with profile command is very complex - unit tests
• Tabs list (terminal-tabs.test.ts)
  • Drag and drop
  • Unsplit
• Terminal editors (terminal-editors.test.ts)
  • Drag and drop between panel and editor
  • Move commands
• Persistence (terminal-persistence.test.ts)
  • Local reconnection
  • Remote reconnection
  • Local revive
  • Remote revive
  • Icons, names
  • Restore order
  • Detach session isn't working - also reattach after kind of tests moving across windows
• Multi-root scenarios?

[Tyriar]

Main goals of this have been accomplished. Layout tests, drag and drop and multi-window tests are a bit tricky to accomplish on smoke tests and mostly test what's already tested.

Multi-root tests deferred in #137747