Select: Unable to leave loading state without re-render?

[GCHQ-Developer-299]

Summary of the bug

Discovered whileintroducing Playground to ic-select

It seems that the loadingHandler function doesn't consider the loading prop changing to false

  @Watch("loading")
  loadingHandler(newValue: boolean): void {
    newValue && this.triggerLoading();
  }

Additionally, updating the loadingLabel prop doesn't change the loading text until loading is toggled off and back on.

🪜 How to reproduce

Tell us the steps to reproduce the problem:

1. Go to the React Playground storybook in Select (single)
2. click to expand the Select
3. in the controls, toggle 'loading' to true
4. you'll see the select switch to a loading state
5. Toggle 'loading' to false
6. The select won't show results, it remains loading. You'll find that expanding and collapsing the select doesn't fix it

📸 Screenshots or code

🧐 Expected behaviour

Switching loading to false should show results / no results. Also, in the Playgrounds (single/searchable select in React, multi-select in Canary) the loadingLabel should update loading text whenever the prop is changed

[ad9242]

This also applies to Multi-Select. After selecting multiple options & then setting loading to true the field contains 1 or more commas

then setting to false the loading state does not clear

If only a single value is selected & then loading is set to true, the placeholder text is black (should be grey) bad:

good:

[ad9242]

may want to consider leaving this until after #2108 is complete

[GCHQ-Developer-718]

Summary of select/loading bugs following testing in Stackblitz and Storybook playground

	Select	Searchable select	Multi-select
Toggling loading prop to false doesn't show results	Present in storybook	Present in storybook	Present in storybook
"Clear selection" button next to placeholder text if loading is changed to true while value is selected	Present in storybook and stackblitz	Not present	Present in storybook and stackblitz
Placeholder text is wrong colour if loading is changed to true while value is selected	Not present	Not present	Present in storybook and stackblitz
Multiple selected values display as commas if loading is changed to true	N/A	N/A	Present in stackblitz
User can use keyboard to select "loading" and "no results found"	Present in stackblitz	Present in stackblitz	Present in stackblitz	User can use search against current options in loading state	N/A	Present in storybook and stackblitz	N/A