Debugging: add integration test with LLDB and some minor tweaks. (#12856)

This PR adds:

- An integration-test that runs LLDB against the Wasmtime CLI to
verify basic debugging functionality, simi

Debugging: add integration test with LLDB and some minor tweaks. (#12856)

This PR adds:

- An integration-test that runs LLDB against the Wasmtime CLI to
verify basic debugging functionality, similar to the existing
native-debug tests.

- A CI job that runs the above in CI.

- Some minor tweaks to the gdbstub debugger design:
- Rather than the initial single-step to get to the first Wasm
instruction where module(s) will be instantiated into the store
and visible to the debugger, we pre-register modules with the
store eagerly. This avoids the slightly hacky flow and also is a
preparation step for `wasmtime serve` debugging, where we can't
single-step into execution eagerly (because execution doesn't
start at all until an HTTP request arrives).
- Add a separate message-printing path for "debugger info messages",
allowing us to print the "debugger is listening on <PORT>" message
without inheriting stderr for the whole debugger component
environment. This message is necessary for the above integration
test (it parses the message to determine when the debuggee is ready).

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