Select OptionHighlighted message leakage

[davep]

The Select widget makes use of OptionList; when the user opens the Select to pick a value, OptionHighlighted messages "leak" out of the Select. This could result in unexpected messages for the developer who has an OptionList and a Select in their DOM and who doesn't expect to actually have two OptionLists that might send messages.

I think we should either stop the OptionHighlighted from bubbling outside of the Select, or we should turn them into SelectionHighlighted if it's felt necessary that they can be handled.

To illustrate:

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import OptionList, Select, Log

class LeakySelectApp(App[None]):

    def compose(self) -> ComposeResult:
        yield Log()
        yield OptionList(*(f"This is option {n}" for n in range(10)))
        yield Select[int](((f"This is selection {n}", n) for n in range(10)))

    @on(OptionList.OptionHighlighted)
    def log_some_option(self, event: OptionList.OptionHighlighted) -> None:
        self.query_one(Log).write_line(f"{event}")

if __name__ == "__main__":
    LeakySelectApp().run()

I think the dev would reasonably expect to only get calls to log_some_option from the OptionList they composed in.

[willmcgugan]

I think we should quell those messages. I can't see a use for an additional message that reports what the user has currently selected.

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