[prism] Avoid allocating Strings by threading 'src lifetime throughout parser state and node types (#745)

* Thread lifetimes through ParserState and associated structs

* [prism] Add lifetimes to formatting functions

* Remove a bunch of _to_string calls and clones

* fmt

Author: reese

librubyfmt/src/comment_block.rs

@@ -24,7 +24,7 @@ impl CommentBlock {
         self.comments.push(line);
     }
 
-    pub fn into_line_tokens(self) -> impl Iterator<Item = ConcreteLineToken> {
+    pub fn into_line_tokens<'src>(self) -> impl Iterator<Item = ConcreteLineToken<'src>> {
         self.comments.into_iter().flat_map(|c| {
             [
                 ConcreteLineToken::Comment { contents: c },

librubyfmt/src/delimiters.rs

@@ -82,25 +82,25 @@ impl BreakableDelims {
         }
     }
 
-    pub fn single_line_open(&self) -> ConcreteLineToken {
+    pub fn single_line_open<'src>(&self) -> ConcreteLineToken<'src> {
         ConcreteLineToken::Delim {
             contents: self.single_line.open,
         }
     }
 
-    pub fn single_line_close(&self) -> ConcreteLineToken {
+    pub fn single_line_close<'src>(&self) -> ConcreteLineToken<'src> {
         ConcreteLineToken::Delim {
             contents: self.single_line.close,
         }
     }
 
-    pub fn multi_line_open(&self) -> ConcreteLineToken {
+    pub fn multi_line_open<'src>(&self) -> ConcreteLineToken<'src> {
         ConcreteLineToken::Delim {
             contents: self.multi_line.open,
         }
     }
 
-    pub fn multi_line_close(&self) -> ConcreteLineToken {
+    pub fn multi_line_close<'src>(&self) -> ConcreteLineToken<'src> {
         ConcreteLineToken::Delim {
             contents: self.multi_line.close,
         }