[2.0.x] Group #include <...> files, update header search paths

[thinkyhead]

Reference: #8585

Update the -I arguments in lpc1768_flag_script.py and move certain LPC1768 headers into subfolders to simplify the include structure a bit.

[teemuatlut]

Ah yeah, the LPC HAL only worked because of this behavior where the compiler found the HAL/SPI.h file even when it probably shouldn't.
Solution could/would be to rename HAL_LPC1768/HAL_SPI.h -> HAL_LPC1768/SPI.h.

[thinkyhead]

.piolibdeps/TMC2130Stepper_ID1493/src/source/TMC2130Stepper.cpp:3:10: fatal error: SPI.h: No such file or directory

Eek. I need to keep reminding myself: Spoofing the libraries into including our own SPI.h via <SPI.h> is necessary because we're doing whole substitution.

It's tough because I get can't get successful compiles due to other causes. I'm going to need a full primer on getting all platforms to compile from those in the know.