Remove the lightbeam backend (#3390)

This commit removes the Lightbeam backend from Wasmtime as per [RFC 14].
This backend hasn't received maintenance in quite some time, and as [RFC
14] indicates this doesn't meet the threshold for keeping the code
in-tree, so this commit removes it.

A fast "baseline" compiler may still be added in the future. The
addition of such a backend should be in line with [RFC 14], though, with
the principles we now have for stable releases of Wasmtime. I'll close
out Lightbeam-related issues once this is merged.

[RFC 14]: https://github.com/bytecodealliance/rfcs/pull/14

crates/c-api/src/config.rs

@@ -20,7 +20,6 @@ wasmtime_c_api_macros::declare_own!(wasm_config_t);
 pub enum wasmtime_strategy_t {
     WASMTIME_STRATEGY_AUTO,
     WASMTIME_STRATEGY_CRANELIFT,
-    WASMTIME_STRATEGY_LIGHTBEAM,
 }
 
 #[repr(u8)]
@@ -114,7 +113,6 @@ pub extern "C" fn wasmtime_config_strategy_set(
     let result = c.config.strategy(match strategy {
         WASMTIME_STRATEGY_AUTO => Strategy::Auto,
         WASMTIME_STRATEGY_CRANELIFT => Strategy::Cranelift,
-        WASMTIME_STRATEGY_LIGHTBEAM => Strategy::Lightbeam,
     });
     handle_result(result, |_cfg| {})
 }