Reorganise https://github.com/cesanta/mongoose/tree/master/tutorials/nxp

Make them look like stm32:

tutorials/nxp/BOARD/{minimal,mcuxpresso}

Many boards that we have there are obsolete, noone uses them. Leave only these boards:

teensy-4.1 (and put only "arduino" project there, so it'd have only teensy-4.1/arduino/) rt1060-evkb rt170-evkb frdm-rt1186 frdm-mcxe247 frdm-mcxn947 frdm-rw612

minimal projects put verbatim, but mcuxpresso ones are big, so put them to the https://github.com/mongoose-examples/BOARD instead and just put a link to the README.