Add visible as kwarg to ViewerElements

[chungmin99]

Allow ViewerElement visibility to be set upon initialization.

Currently, all elements are always set to visible.

However, it might be good to intentionally make elements invisible from the get-go, like the dropdown example below. This is not possible in the current code, because ViewerElement's gui_handle is initialized after the pipeline.

Corresponding code is also attached.

self.viewer_0_selection = ViewerDropdown(name="Options", default_value="1", options=["1", "2"])
self.viewer_1_button_1 = ViewerButton(name="Button 1", visible=True,  cb_hook=lambda _: None)
self.viewer_1_button_2 = ViewerButton(name="Button 2", visible=False, cb_hook=lambda _: None)

# Change visibility of buttons based on dropdown value
def swap_visible_button(dropdown: ViewerDropdown):
    if dropdown.value == "1":
        self.viewer_1_button_1.set_visible(True)
        self.viewer_1_button_2.set_visible(False)
    else:
        self.viewer_1_button_1.set_visible(False)
        self.viewer_1_button_2.set_visible(True)
self.viewer_0_selection.cb_hook = swap_visible_button

Screen.Recording.2024-01-05.at.11.36.48.AM.mov

[kerrj]

lgtm