Ensure MV2/MV3 sidebar controller behavior is consistent

[twschiller]

Context

• In general, the top-level frame should control the sidebar. In these cases, the use must use target: top on the brick when calling it from a frame
• However, some operations might be safe to call from a frame (e.g., open sidebar), and we might not want to require explicitly using target: top
• However, in MV3, opening the sidebar must be done from a user gesture, so we have to be careful about where the event is actually run

Sidebar Controller Methods

Test Mods:

• Test mod: @pixies/test/frame-sidebar-actions
• For use with https://pbx.vercel.app/ frames builder page

Method Behavior Inventory

• showSidebar
  • MV2 behavior: ✅ can run in any frame
  • MV3 behavior: 🟡 can run in any frame -- shows the user gesture dialog in the frame if there's too long of a delay
• hideSidebar
  • MV2 behavior: ✅ can run in any frame
  • MV3 behavior: ✅ can run in any frame
• showSidebarForm
  • MV2 behavior: intentional BusinessError when running from iframe
  • MV3 behavior: ✅ same as MV2
• showTemporarySidebarPanel: Fixed in 00ea332
  • MV2 behavior: errors out. The sidebar opens, but no panel is shown with error "Cannot add temporary sidebar panel if the sidebar is not visible" (like the form, we should prevent it from being run from a frame)
  • MV3 behavior: 🟡 shows the document -- but does not continue after closing/submitting the panel

Out of Scope

• The Chromium Sidepanel on MS Edge handle switching tabs differently than Chrome: Tab-specific sidePanel inconsistencies when opening new tabs/switching tabs w3c/webextensions#588

Related Issues/PRs

• #8219: don't let frames control sidebar panel via setPanels #8225