[1.1.x] Platformio - automate build & environment selection

[Bob-the-Kuhn]

This is the 1.1.x version of PR #10561 which is the bugfix-1.1.x version of PR #10503. See PR #10503 for details.

The changes to implement this feature are:

• copy auto_build.py from bugfix-1.1.x into 1.1.x
• copy process-palette.json from bugfix-1.1.x into 1.1.x
• copy the comments in pins.h from bugfix-1.1.x into 1.1.x - I had to re-arrange the INCLUDES and DEFINES in the RAMPS section at the beginning to be compatible with the auto-build script. I ended up making the RAMPs section look like bugfix-1.1.x. The before and after may look different but they are functionally the same.
• replace platformio.ini with the one from from bugfix-1.1.x into 1.1.x. After a bunch of re-arranging I was convinced that the only real difference between the two was formatting. After it was all over 1.1.x gained the Melzi optiboot section. That makes it 100% compatible with the current 1.1.x and with the auto-build script.

This has been tested on a 2560 board and a 1284 board.

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This PR is against a released branch. That normally isn't done. In this case it may make sense because it results in the current release and the two bugfixes all supported by the new script.

It also makes the new doc page I'm working on easier to write.

[thinkyhead]

This PR is against a released branch. That normally isn't done. In this case it may make sense because it results in the current release and the two bugfixes all supported by the new script.

There's no point. It's not going to be part of a tagged release, and will only complicate matters when we merge bugfix into 1.1.x. …… Which will only happen when #10446 is fixed …… and I'm totally stumped on that one so far.

[Bob-the-Kuhn]

OK - this PR is dead.

I'll try to have the doc changes ready for comments later today.