Auto merge of #53679 - japaric:cortex-r, r=alexcrichton

Auto merge of #53679 - japaric:cortex-r, r=alexcrichton

add more Cortex-R targets

This expands on PR #53663 to complete the set of Cortex-R targets and builds
rust-std components for them.

r? @alexcrichton

each extra rust-std component (there's 4 of them) takes about 3 minutes to build
on my local machine. In terms of stability (LLVM codegen bugs) these new targets
should be as stable as the Cortex-M ones (e.g. `thumbv7m-none-eabi`).

If the extra build time is too much we can leave the rust-std components out for
now

closes #53663
cc @paoloteti