Inline some `Symbol` functions

compiler/rustc_span/src/symbol.rs

diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 8e23e29..ed2167a 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -2655,6 +2655,7 @@ pub const fn new(n: u32) -> Self {
 
     /// Maps a string to its interned representation.
     #[rustc_diagnostic_item = "SymbolIntern"]
+    #[inline]
     pub fn intern(str: &str) -> Self {
         with_session_globals(|session_globals| session_globals.symbol_interner.intern_str(str))
     }
@@ -2667,6 +2668,7 @@ pub fn intern(str: &str) -> Self {
     /// interner. Interners are long-lived, and there are very few of them, and
     /// this function is typically used for short-lived things, so in practice
     /// it works out ok.
+    #[inline]
     pub fn as_str(&self) -> &str {
         with_session_globals(|session_globals| unsafe {
             std::mem::transmute::<&str, &str>(session_globals.symbol_interner.get_str(*self))