chore: Use .includes and .startsWith, not .indexOf (#7936)

Easier to read than the diverse collection of `=== 0` and `!== -1` and `> -1` tests.

generators/python/procedures.ts

@@ -27,7 +27,7 @@ export function procedures_defreturn(block: Block, generator: PythonGenerator) {
   for (const variable of usedVariables) {
     const varName = variable.name;
     // getVars returns parameter names, not ids, for procedure blocks
-    if (block.getVars().indexOf(varName) === -1) {
+    if (!block.getVars().includes(varName)) {
       globals.push(generator.getVariableName(varName));
     }
   }

generators/python/python_generator.ts

@@ -243,8 +243,8 @@ export class PythonGenerator extends CodeGenerator {
 
     // Follow the CPython behaviour of repr() for a non-byte string.
     let quote = "'";
-    if (string.indexOf("'") !== -1) {
-      if (string.indexOf('"') === -1) {
+    if (string.includes("'")) {
+      if (!string.includes('"')) {
         quote = '"';
       } else {
         string = string.replace(/'/g, "\\'");

generators/python/text.ts

@@ -32,7 +32,7 @@ export function text_multiline(
 ): [string, Order] {
   // Text value.
   const code = generator.multiline_quote_(block.getFieldValue('TEXT'));
-  const order = code.indexOf('+') !== -1 ? Order.ADDITIVE : Order.ATOMIC;
+  const order = code.includes('+') ? Order.ADDITIVE : Order.ATOMIC;
   return [code, order];
 }