swift-wasm-DEVELOPMENT-SNAPSHOT-2023-11-01-a

Fix calling convention mismatch for debugger utility functions

This is the 3rd attempt to fix the mismatch, where the actual definition
(e.g. `swift_retainCount`) are defined with C calling-convention and the
callers wrongly expect Swift calling-convention.

The 1st fix broke ABI compatibility by introducing new symbol references
from app-side without any availability checks.
The 2nd fix broke lldb's retain counting feature due to new x-ref to
Clang module in serialized function body by `@_alwaysEmitIntoClient`.

This attemps to avoid introducing serialized x-ref to Clang module by
using new `@extern(c)` attribute.

Co-authored-by: Karoy Lorentey <[email protected]>