Remove several unused packages

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Overview

These commits deselect a bunch of unused packages in an attempt to free up some filesystem space. (See Opentrons/opentrons#8184.)

Unfortunately, I still don't think this is enough for a top-level make push to succeed, so Opentrons/opentrons#8184 will stay open.

Changelog

• Removed Python packages for JSON-RPC.
  • Per @sfoster:

    it was a first attempt at making a nice network-transparent interface to the hardware controller for test engineering and others who want to directly interact with it

    i think we're moving away from the concept, you can remove it

  • Also removed chardet, a dependency of this.
• Removed pyserial-asyncio. I couldn't find any instance of import serial_asyncio in Opentrons/opentrons.
• Removed json-c, a library that isn't mandated by anything else that we have installed.
• Removed a bunch of nginx modules that appeared unused to me, judging by our nginx.conf.
• Removed sl. 😢

Review requests

Do any of the removed packages strike you as something that we should definitely not remove?

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Ideas for further work:

• This PR added git, curl, and wget.

  Do we really need git? Do we really need both curl and wget, or can we just pick one?

• Busybox has its own implementations of curl and/or wget (can't remember which, exactly). So we have two implementations installed. Can we get rid of one? Are we accidentally doing this with any other commands?

• Should we strip test files from Python packages, sort of automating the workaround in bug: robot's filesystem is out of space,make push sometimes fails opentrons#8184?

[sfoster1]

This looks good but I think there's more we can do like,

• Strip out all the bluetooth stuff. this was a temporary experiment that at this point I think is not going to happen
• if busybox has a curl let's use that; wget can still be useful, but i don't really care whether it happens or not
• i do not remember at all why we added git, let's not
• i doubt we need screen or tmux but they're also tiny so whatever

Stripping as much non-critical content from the python stuff is absolutely a good idea. We may also find it useful to install them as gzipped wheels to save disk space.

[sfoster1]

huh, stuff like this usually doesn't make it into a defconfig, wonder if nginx is doing something weird to parse these. would expect them to be BR2_PACKAGE_NGINX_HTTP_GZIP_MODULE=n and so on

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Yeah, it is weird and mysterious.

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Aggregating those further ideas in #144.