Board selector should be usable with the keyboard

[AlbyIanna]

Describe the problem

The Board Selector is only partially usable via the keyboard.

To reproduce

Using the keyboard only:

• try to focus on the board selector
• open it with either ENTER or SPACEBAR
• close it with ESCAPE
• select all the items in the dropdown
  You won't be able to do everything 🐛

When the Select Other Board and Port dialog is open, it's not possible to select a board or a port from the lists only using a keyboard.

Expected behavior

• focusing on the board selector should show a focus outline (related: Drop-down menus are not highlighted when selected #1680)
• when the board selector is focused it should be openable by pressing ENTER or SPACEBAR
• when the board selector is open, it should be possible to close it pressing ESCAPE
• selecting an item in the board selector and pressing ENTER or SPACEBAR should trigger the action

When the Select Other Board and Port dialog is open, it should be possible to select a board a port only using a keyboard.

Arduino IDE version

any

Operating system

N/A

Operating system version

any

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest nightly build
• My report contains all necessary details