Fix handling of class property value this in module transforms. (#9857)

Prevent module transforms from rewriting `this` to `void 0` when found in the values of private class properties.  Add tests to prevent regressions.

packages/babel-plugin-transform-modules-commonjs/test/fixtures/class-properties/private-method/input.mjs

@@ -0,0 +1,5 @@
+class Example {
+  #method() {
+    console.log(this);
+  }
+}

packages/babel-plugin-transform-modules-commonjs/test/fixtures/class-properties/private-method/output.js

@@ -0,0 +1,8 @@
+"use strict";
+
+class Example {
+  #method() {
+    console.log(this);
+  }
+
+}