Fix module graph patching: use version-agnostic byte search instead o…

…f struct parsing

The CompiledModuleGraphFile struct layout changed between Bun 1.2.x (36 bytes)
and 1.3.x (52 bytes), causing the module-by-module parser to fail with a
non-integer module count (1040/36 = 28.89).

Replace the struct-aware module parsing with a simple byte search in the raw
string data region. The undici patch is a same-size in-place replacement, so
no module struct knowledge is needed. The module list and offsets are passed
through unchanged.

Also removes the unused librust_pty patching code (was never triggered).