* feat: relocate riscv isr to iram
Previously, the trap vector itself and its immediate callees
(`_start_trap` and `_start_trap_rust_hal`) were located in the mapped
instruction flash range `0x420..`, increasing cache pressure and adding
variable latency to the very beginning of the interrupt/exception
service flow.
This change places those routines in iram directly:
```
Num: Value Size Type Bind Vis Ndx Name
48177: 40380280 2428 FUNC GLOBAL DEFAULT 6 _start_trap_rust_hal
48197: 40380bfc 54 FUNC GLOBAL DEFAULT 6 _start_trap_rust
48265: 40380200 0 FUNC GLOBAL DEFAULT 6 _vector_table
48349: 40380100 0 NOTYPE GLOBAL DEFAULT 6 default_start_trap
48350: 40380100 0 NOTYPE GLOBAL DEFAULT 6 _start_trap
```
As seen via `readelf -W -s -C ./target/riscv32imc-unknown-none-elf/debug/examples/gpio_interrupt | grep -E _start_trap\|_vector\|Ndx`
* feat(riscv): place .trap in RAM
This change follows through on relocating the `_vector_table`,
`_start_trap`, and `_start_trap_rust` functions for all present
build/link modes for the 'c2, 'c3, 'c6, and 'h2.
It has been tested by running the `software_interrupts` example for the
'c3 in direct-boot and esp-bootloader contexts, but I wasn't able to
identify how to run the `mcu-boot` mode for the 'c3, nor do I have
present access to any of the other devices for testing.
* docs: Update CHANGELOG.md
171e66e87a