The GDB-stub for Wasm debugging (which builds with the flag
v8_enable_wasm_gdb_remote_debugging) doesn't build anymore after a few changes
in the interface of wasm::DebugInfo.
This CL fixes the build, and also adds a few small changes to the protocol.

Change-Id: I250a8c86fd83048434e68cbdc5cb8ae243577393
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2571341Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Philip Pfaffe <pfaffe@chromium.org>
Commit-Queue: Paolo Severini <paolosev@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#71669}