Remove seldom-used boards platforms from the primary package index

[probonopd]

Is your feature request related to a problem? Please describe.

This is the flipside of arduino/arduino-ide#326.

I'm always frustrated when the Boards Manager presents me with exotic, expensive boards not many people are using. These could be added by the few users who are using them via a JSON file if needed.

As @per1234 pointed out,

Arduino has already made it extremely easy to install support for 3rd party boards platforms. It's no great hardship to add a URL to your preferences.

So I think only the most popular boards (the ones sold by the millions) should show up there by default. Not "POC" ones very few people possess.

Describe the solution you'd like

Remove

because they feel like advertising to me.

Describe alternatives you've considered

I don't know how to remove them manually.

Additional context

The freed-up space could be used for the most popular boards in the world, which is a separate feature request:

https://github.com/arduino/arduino-ide/issues/326

[nielsnl68]

I would say show only the boards that you really have. And hide all others until you going to search for the board that you want to use.