feat(esm): convert to esm (#2569)

for #2543

BREAKING CHANGE: semantic-release is now ESM-only. since it is used through its own executable, the impact on consuming projects should be minimal

BREAKING CHANGE: references to plugin files in configs need to include the file extension because of executing in an ESM context

test/get-next-version.test.js

@@ -1,6 +1,6 @@
-const test = require('ava');
-const {stub} = require('sinon');
-const getNextVersion = require('../lib/get-next-version');
+import test from 'ava';
+import {stub} from 'sinon';
+import getNextVersion from '../lib/get-next-version.js';
 
 test.beforeEach((t) => {
   // Stub the logger functions