fix: Revert drop down and widget div PRs

[BenHenning]

The basics

• I @microbit-matt-hillsdon and @microbit-robert validated my changes

The details

Resolves

Fixes part of #9221 (or, rather, puts things back into a less broken state)

Proposed Changes

This reverts #9213 and #9216.

Reason for Changes

The "fixed" world is more broken than before, or at least the breakages from before are better understood.

Fundamentally, there are several classes of edge cases for ephemeral focus with widget and drop-down divs that may not have single solutions. A more carefully thought out solution is required at this point, and there isn't sufficient time to safely land such a change ahead of the 12.2 release. It's preferable to revert the attempts at fixing these classes of issues since the previous breakages were harder to hit than the new ones.

#9221 is tracking longer term fixes.

Test Coverage

N/A -- This is a revert.

Documentation

N/A -- This is a revert.

Additional Information

This PR was produced with two git revert commands and has no other changes.

RaspberryPiFoundation/blockly-keyboard-experimentation#563 will need to be reopened after this PR merges since the problems that issue tracked will be reintroduced.

[BenHenning]

PTAL @gonfunko but also please hold on merging until @microbit-matt-hillsdon has a chance to confirm the revert.

[microbit-matt-hillsdon]

Looks good, thanks.

I tested MakeCode locally linked to a checkout of this PR and as expected we have RaspberryPiFoundation/blockly-keyboard-experimentation#563 back but the combined widget/dropdown div field editors are working well again for keyboard users.

We also speculatively tested an equivalent pair of git reverts earlier today and all seemed well.

I've also updated our preview deployment of MakeCode to include this PR so you can try it there too (enable Keyboard Controls via settings cog or first tab stop). Simple test program as JavaScript:

input.onButtonPressed(Button.A, function () {
    led.plot(2, 3)
    basic.pause(500)
})

[BenHenning]

Thanks @microbit-matt-hillsdon and @microbit-robert for help with the testing.

Going ahead and merging since this puts Blockly back to an expected good (enough) state for the release.