Extend Selection Menu to allow text selection

[marthasharkey]

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[kazcw]

The isTextDropdown mode changes a lot of the behavior of the SelectionMenu; the divergence will only increase in the future--we also have more changes planned for this type of text dropdowns (e.g. filtering mentioned in #11335). As such, instead of adding a new mode to SelectionDropdown, let's create a new component for text selection dropdowns.

[kazcw]

Since we are using both the keys and the values of data.value.axis, using Object.entries might be simpler, and would avoid the type cast.

[kazcw]

Not-present (undefined) or null would have the same meaning--let's avoid a distinction without a difference.

Suggested change

	heading?: string | null
	heading?: string | undefined

[kazcw]

Instead of the isTextDropdown field, let's introduce a separate type:

export interface TextSelectionMenu {
  type: 'textSelectionMenu'
  selected: Ref<string>
  title?: string
  options: Record<string, TextSelectionMenuOption>
  heading?: string
}

---

The reason for the type field approach is probably not apparent--it fits into my plan for the ToolbarItem types (as we add more and their definitions get more complex):

Eventually, every type will have a type field that must contain a specific value if present; however, the field will be optional for any type that can be recognized by its fields, to allow concise toolbar definitions.

So far, every type has had distinctive enough fields that we haven't needed to make any type fields required (and I haven't got around to defining optional type fields). The new TextSelectionMenu has similar fields to the normal SelectionMenu, so its type field is not optional.

[marthasharkey]

ok! Thanks, I wasn't sure if it was best to adapt the current dropdown or make a new one so I'll separate it now!