fix(eslint-plugin): [prefer-readonly] disable checking accessors (#8300)

* Disable checking accessors for prefer-readonly

* Granular accessor tests

* Update packages/eslint-plugin/src/rules/prefer-readonly.ts

* fix: formatting and || for isModifierFlagSet suggestion

---------

Co-authored-by: Josh Goldberg ✨ <[email protected]>

Author: Jamesernator

Diff for: packages/eslint-plugin/src/rules/prefer-readonly.ts

@@ -299,7 +299,10 @@ class ClassScope {
         tsutils.isModifierFlagSet(node, ts.ModifierFlags.Private) ||
         node.name.kind === ts.SyntaxKind.PrivateIdentifier
       ) ||
-      tsutils.isModifierFlagSet(node, ts.ModifierFlags.Readonly) ||
+      tsutils.isModifierFlagSet(
+        node,
+        ts.ModifierFlags.Accessor | ts.ModifierFlags.Readonly,
+      ) ||
       ts.isComputedPropertyName(node.name)
     ) {
       return;

Diff for: packages/eslint-plugin/tests/rules/prefer-readonly.test.ts

@@ -717,6 +717,26 @@ class Foo {
         }
       }
     `,
+    `
+      class TestStaticPrivateAccessor {
+        private static accessor staticAcc = 1;
+      }
+    `,
+    `
+      class TestStaticPrivateFieldAccessor {
+        static accessor #staticAcc = 1;
+      }
+    `,
+    `
+      class TestPrivateAccessor {
+        private accessor acc = 3;
+      }
+    `,
+    `
+      class TestPrivateFieldAccessor {
+        accessor #acc = 3;
+      }
+    `,
   ],
   invalid: [
     {