reorg: remove dispatch.ts, move signals, factor out web utils (#4316)

- moves signal definition from "cli/js/process.ts" to "cli/js/signals.ts"
- removes "cli/js/dispatch.ts"
- removes "cli/js/types.ts"
- moves web specific utilities to "cli/js/web/util.ts"

cli/js/util.ts

@@ -1,5 +1,4 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { TypedArray } from "./types.ts";
 
 let logDebug = false;
 let logSource = "JS";
@@ -80,30 +79,6 @@ export function notImplemented(): never {
   throw new Error("Not implemented");
 }
 
-// @internal
-export function unreachable(): never {
-  throw new Error("Code not reachable");
-}
-
-const TypedArrayConstructor = Object.getPrototypeOf(Uint8Array);
-export function isTypedArray(x: unknown): x is TypedArray {
-  return x instanceof TypedArrayConstructor;
-}
-
-// @internal
-export function requiredArguments(
-  name: string,
-  length: number,
-  required: number
-): void {
-  if (length < required) {
-    const errMsg = `${name} requires at least ${required} argument${
-      required === 1 ? "" : "s"
-    }, but only ${length} present`;
-    throw new TypeError(errMsg);
-  }
-}
-
 // @internal
 export function immutableDefine(
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -118,45 +93,3 @@ export function immutableDefine(
     writable: false
   });
 }
-
-// Returns values from a WeakMap to emulate private properties in JavaScript
-export function getPrivateValue<
-  K extends object,
-  V extends object,
-  W extends keyof V
->(instance: K, weakMap: WeakMap<K, V>, key: W): V[W] {
-  if (weakMap.has(instance)) {
-    return weakMap.get(instance)![key];
-  }
-  throw new TypeError("Illegal invocation");
-}
-
-/**
- * Determines whether an object has a property with the specified name.
- * Avoid calling prototype builtin `hasOwnProperty` for two reasons:
- *
- * 1. `hasOwnProperty` is defined on the object as something else:
- *
- *      const options = {
- *        ending: 'utf8',
- *        hasOwnProperty: 'foo'
- *      };
- *      options.hasOwnProperty('ending') // throws a TypeError
- *
- * 2. The object doesn't inherit from `Object.prototype`:
- *
- *       const options = Object.create(null);
- *       options.ending = 'utf8';
- *       options.hasOwnProperty('ending'); // throws a TypeError
- *
- * @param obj A Object.
- * @param v A property name.
- * @see https://eslint.org/docs/rules/no-prototype-builtins
- * @internal
- */
-export function hasOwnProperty<T>(obj: T, v: PropertyKey): boolean {
-  if (obj == null) {
-    return false;
-  }
-  return Object.prototype.hasOwnProperty.call(obj, v);
-}