Update dependencies and generated files

Adds `critical-section` feature to enable enabling/disabling interrupts
on a single HART (via `riscv::critical_section`).

A custom `critical_section` impl could enable enabling/disabling
interrupts on multiple HARTs.

Generates updated source files from SVD file.

Clears cargo lint warnings by removing deprecated attributes.

Update svd2rust and remove riscv-rt dependency

Fixes https://github.com/riscv-rust/gd32vf103-pac/issues/3

Update riscv-rt to v0.7.1

readme: fix link