[ES|QL] PromQL pretty-printing support (elastic#247399)

## Summary

Partially addresses elastic#243932

Adds ability to transforms a PromQL AST back to text: pretty-print.
Supports basic pretty printing where the whole PromQL query is printed
on a single line with minimal whitespace.


### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

Author: vadimkibana

src/platform/packages/shared/kbn-esql-language/src/promql/builder/builder.ts

@@ -236,17 +236,25 @@ export namespace PromQLBuilder {
         };
       };
 
+      /**
+       * Create a string literal.
+       *
+       * @param valueUnquoted - The unquoted string value (e.g., 'hello' not '"hello"')
+       * @param rawValue - Optional raw value as it appeared in source (used by parser).
+       *                   If not provided, the printer will handle quoting/escaping.
+       * @param fromParser - Optional parser fields
+       */
       export const string = (
-        value: string,
         valueUnquoted: string,
+        rawValue?: string,
         fromParser?: Partial<AstNodeParserFields>
       ): PromQLStringLiteral => {
         return {
           dialect: 'promql',
           type: 'literal',
           literalType: 'string',
-          name: value,
-          value,
+          name: rawValue ?? valueUnquoted,
+          value: rawValue ?? valueUnquoted,
           valueUnquoted,
           ...PromQLBuilder.parserFields(fromParser),
         };

src/platform/packages/shared/kbn-esql-language/src/promql/parser/cst_to_ast_converter.ts

@@ -596,16 +596,17 @@ export class PromQLCstToAstConverter {
       return this.fromStringToken(token.symbol);
     }
 
-    return PromQLBuilder.expression.literal.string(ctx.getText(), '', this.getParserFields(ctx));
+    const text = ctx.getText();
+    return PromQLBuilder.expression.literal.string('', text, this.getParserFields(ctx));
   }
 
   private fromStringToken(token: antlr.Token): ast.PromQLStringLiteral {
     const text = token.text ?? '';
     const valueUnquoted = this.unquoteString(text);
 
     return PromQLBuilder.expression.literal.string(
-      text,
       valueUnquoted,
+      text,
       this.createParserFieldsFromToken(token)
     );
   }