Implement assumptions defined in the babel/rfcs#5 RFC

- `mutableTemplateObject` and `ignoreToPrimitiveHint` (#12408)
- `setClassMethods` (#12407)
- `setComputedProperties` (#12490)
- `ignoreFunctionLength` (#12491)
- `noDocumentAll` (#12481)
- `iterableIsArray` and `arrayLikeIsIterable` (#12489)
- `pureGetters` (#12504)
- `skipForOfIteratorClosing` (#12496)
- `objectRestNoSymbols`, `setSpreadProperties` and `pureGetters` (#12505)
- `noNewArrows` (#12613, #12793)
- `setPublicClassFields` and `privateFieldsAsProperties` (#12497)
- `constantReexports` and `enumerableModuleMeta` (#12618)
- `constantSuper`, `superIsCallableConstructor` and `noClassCalls` (#12726)

Co-authored-by: Justin Ridgewell <justin@ridgewell.name>
Co-authored-by: Huáng Jùnliàng <JLHwung@users.noreply.github.com>

packages/babel-plugin-transform-destructuring/test/fixtures/assumption-arrayLikeIsIterable/simple/exec.js

@@ -0,0 +1,6 @@
+var o = { 0: "a", 1: "b", 2: "c", length: 3 };
+
+var [first, ...rest] = o;
+
+expect(first).toBe("a");
+expect(rest).toEqual(["b", "c"]);

packages/babel-plugin-transform-destructuring/test/fixtures/assumption-arrayLikeIsIterable/simple/input.js

@@ -0,0 +1 @@
+var [first, ...rest] = o;

packages/babel-plugin-transform-destructuring/test/fixtures/assumption-arrayLikeIsIterable/simple/output.js

@@ -0,0 +1,4 @@
+var _o = o,
+    _o2 = babelHelpers.maybeArrayLike(babelHelpers.toArray, _o),
+    first = _o2[0],
+    rest = _o2.slice(1);