Update the Inst::name() function to be const

This can be `const` because it just returns a static string value.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/inst.rs

@@ -69,7 +69,8 @@ pub enum Inst {
 // impl Inst
 //
 impl Inst {
-    pub fn name(&self) -> &'static str {
+    /// Gets the printable name of this instruction.
+    pub const fn name(&self) -> &'static str {
         match self {
             Inst::PushSym(_) => "PUSH_SYM",
             Inst::PushConst(_) => "PUSH_CONST",