define `const compressed_string_t *` as `mp_rom_error_text_t`?

[dhalbert]

Can we define const compressed_string_t * as mp_rom_error_text_t to reduce code skew from MicroPython, so that functions take mp_rom_error_text_t as an argument? @jepler has remarked on this, and @dhalbert was reminded of that during #8508.