Run process() task from ITCM

[jordens]

• To get most out of the faster (than flash) ITCM, the 64 bit dual issue pipeline, and the cortex-m7 instruction schedule coming with rust 1.52
• needs a custom pre_init (see [RFC] #[ramfunc] rust-embedded/cortex-m-rt#100 https://github.com/imxrt-rs/imxrt-rt/blob/6e8ec474abf88d769222df920f47ab057eda92d1/src/reset.c#L43-L60 https://github.com/mciantyre/teensy4-rs/blob/master/bin/start.s)
• The inlining in release mode looks good enough to not require to much proliferation of link_section attributes beyond the process task itself.