Add architecture-independent exception handling APIs sufficient for hyperlight-wasm

Currently, hyperlight-guest exposes an architecture-specific way of overriding certain raw exception handler on x86-64 that is used by hyperlight-wasm. Really, we should instead have architecture-independent hooks for
- Intercepting certain kinds of misbehaviour-indicating exceptions (e.g. FP divide by zero, access to guard regions)
- Support for the virtual memory primitives that hyperlight-wasm needs in hyperlight-guest (e.g. zero-on-first-read regions, copy-on-write images, guard regions)

Start by inspecting the architecture-specific raw exception handler in hyperlight-guest and how hyperlight-wasm uses it. Then trace the virtual memory primitives required by hyperlight-wasm, including zero-on-first-read regions, copy-on-write images, and guard regions. Done means hyperlight-guest exposes architecture-independent hooks and primitives covering these requirements.

索引モデルが issue の本文から書いたものです。