Discovery cleanup

[kittaakos]

Motivation

This is another variant of #1167.

There is a bug with #1167 that can be reproduced on my Windows machine with the following steps:

• IDE2 is up and running, a board is connected and recognized by IDE2; it's the selected board,
• Stop IDE2,
• Start IDE2 (You can see the board is connected from the dropdown),
• Disconnect the board when the Downloading .... notification message (this is when IDE2 initializes the core client),
• Core client reinitialization is done, the board is not connected, but IDE2 still shows it as a connected board.

This PR fixes this issue, but IDE2 must stop the board discovery before re-initializing the core client and restarting after it. WheIDE2 stops the board discoveryE2 before the re-init; zero available board and ports must be broadcasted to the frontends. So users will see a disconnect/reconnect board before/after the index update and the core client re-init.

See it in action:

stop-discovery-during-client-reinit.mp4

Change description

Other information

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[per1234]

No matter what sort of rude user behavior I throw at the IDE, the discovery has worked perfectly 100% of the time during my tests of this PR.

However, I am not confident that I have effectively verified the bug fix this is intended to provide because I was able to reproduce it only very rarely with the build for #1167.

[kittaakos]

Follow-up: #1186