The new JIT::GDB namespace enables registering JITted objects into GDB
dynamically.
Its clients just have to ensure the memory they give to
`register_into_gdb` is in a format that GDB can understand, either by
generating an object file in memory with debug info + symbols or by
registering a custom debug info parser.
None of these are implemented by this API; it only implements the
registering part and lets the client to choose the data format.
GDB JIT Interface:
https://sourceware.org/gdb/current/onlinedocs/gdb.html/JIT-Interface.html#JIT-Interface
Things to take into account from v8's docs, some of which we may
improve: https://v8.dev/docs/gdb-jit#known-limitations
