Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

crates/runtime/src/traphandlers/macos.rs

@@ -149,7 +149,7 @@ use mach_addons::*;
 pub enum Void {}
 /// For now this is basically unused, we don't expose this any more for
 /// Wasmtime on macOS.
-pub type SignalHandler<'a> = dyn Fn(Void) -> bool + 'a;
+pub type SignalHandler<'a> = dyn Fn(Void) -> bool + Send + Sync + 'a;
 
 /// Process-global port that we use to route thread-level exceptions to.
 static mut WASMTIME_PORT: mach_port_name_t = MACH_PORT_NULL;

crates/runtime/src/traphandlers/unix.rs

@@ -7,7 +7,7 @@ use std::ptr::{self, null_mut};
 
 /// Function which may handle custom signals while processing traps.
 pub type SignalHandler<'a> =
-    dyn Fn(libc::c_int, *const libc::siginfo_t, *const libc::c_void) -> bool + 'a;
+    dyn Fn(libc::c_int, *const libc::siginfo_t, *const libc::c_void) -> bool + Send + Sync + 'a;
 
 static mut PREV_SIGSEGV: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();
 static mut PREV_SIGBUS: MaybeUninit<libc::sigaction> = MaybeUninit::uninit();

crates/runtime/src/traphandlers/windows.rs

@@ -6,7 +6,8 @@ use winapi::um::winnt::*;
 use winapi::vc::excpt::*;
 
 /// Function which may handle custom signals while processing traps.
-pub type SignalHandler<'a> = dyn Fn(winapi::um::winnt::PEXCEPTION_POINTERS) -> bool + 'a;
+pub type SignalHandler<'a> =
+    dyn Fn(winapi::um::winnt::PEXCEPTION_POINTERS) -> bool + Send + Sync + 'a;
 
 pub unsafe fn platform_init() {
     // our trap handler needs to go first, so that we can recover from