fix: Replace ad-hoc GCC -Wformat suppression with bytes_to_lowercase_hex

check_bytes_constraint() and format_bytes() in the generic TX parser
rendered byte values as "0x" + hex via snprintf("0x%.*h", ...) and
silenced GCC with a localized -Wformat suppression because the %h
length-prefixed hex specifier is a BOLOS extension the compiler does
not recognize. The pragma block silences any -Wformat issue inside
its scope, hiding genuine format/argument mismatches that may arise
from later edits in the same window.

Prefix the destination buffer with "0x" and call
bytes_to_lowercase_hex() to fill the rest, which preserves the
lowercase casing the original %h specifier produced (and that the
existing GCS snapshots match) without needing a diagnostic
suppression.

(cherry picked from commit 22cd0cfb75bbc900128e05e911553b1b5263f8e7)