Add some more #[inline] annotations for trivial functions (#2817)

Looking at some profiles these or their related functions were all
showing up, so this commit adds `#[inline]` to allow cross-crate
inlining by default.

crates/runtime/src/instance.rs

@@ -970,6 +970,7 @@ impl InstanceHandle {
     /// of the internals, there's no lifetime tracking around its validity.
     /// You'll need to ensure that the returned handles all go out of scope at
     /// the same time.
+    #[inline]
     pub unsafe fn clone(&self) -> InstanceHandle {
         InstanceHandle {
             instance: self.instance,

crates/runtime/src/vmcontext.rs

@@ -490,17 +490,20 @@ mod test_vmshared_signature_index {
 
 impl VMSharedSignatureIndex {
     /// Create a new `VMSharedSignatureIndex`.
+    #[inline]
     pub fn new(value: u32) -> Self {
         Self(value)
     }
 
     /// Returns the underlying bits of the index.
+    #[inline]
     pub fn bits(&self) -> u32 {
         self.0
     }
 }
 
 impl Default for VMSharedSignatureIndex {
+    #[inline]
     fn default() -> Self {
         Self::new(u32::MAX)
     }