add support for initialize hook

[iambumblehead]

this PR adds support for the initialize hook: https://nodejs.org/api/esm.html#initialize

Essentially, with node v20.6 esmock does not need to be called with "--loader" and instead esmock creates its own message channel and script-registers the loader to the channel itself.

[iambumblehead]

The newer initialize hook will really simplify many things and allow us to remove global variables and other things. For now though, things will get complicated.

[iambumblehead]

This PR has a few major issues but is almost working. Observe current issues with esmock.node.global.test.js

./tests/tests-node/

npm run test-one esmock.node.global.test.js
npm run test-one-no--loader esmock.node.global.test.js

Main problem: currently, loader hooks engage three times and process files three times. This happens when "initialized" loader exports hooks used by "--loader" loader. If we did not need backward-compatibility, places needed by "--loader" could be removed and we would be done,

• 'esmock.js' should not export hook definitions unless "--loader" is used export * from './esmockLoader.js'
• module.register should only be called one time by the top level caller, if no loader is already introduced by "--loader"
• the error message should explain --loader is used with older versions of node

[iambumblehead]

yikes node v20's globalPreload mechanism esmock uses to message the loader was removed this morning! nodejs/node#49144

[iambumblehead]

cautiously, this branch is mostly working... other things to consider adding here before this branch will be ready,

• update the README, remove package.json example and include some message that links to the wiki for demonstrations of "--loader" that are required by older versions of node
• update the error message that is thrown when loader is undefined, message something like "node versions earlier than v18.6 require the --loader hook; for more details see https://github.com/iambumblehead/esmock/wiki"
• esmockLoader.js should be included and not-deleted from the published directory of files
• tests verifying "import.meta.resolve" should be removed and possibly replaced with tests verifying esmock without a --loader when node version is greater than 20.6
• we should try re-enabling the latest node 18 for the unit-tests, in case any changes are back-ported to appear in newer versions of node 18. If the edge-case windows test fails there we should consider disable that specific test when for windows and node version 18.

[iambumblehead]

package.json scripts in the test folders are updated with patterns like this one used by the mocha folder

"scripts": {
  "isnodelt20_6": "node -e \"(([mj, mn]) => (+mj < 20 || (+mj === 20 && +mn < 6)))(process.versions.node.split('.')) || process.exit(1)\"",
  "test:loader": "mocha --loader=esmock",
  "test:current": "mocha",
  "test": "npm run test:loader && npm run isnodelt20_6 || npm run test:current"
}

This is kind of noisy however works well with windows and npm and, for newer versions of node, runs tests without --loader=esmock. When support for node18 is dropped, a lot of noise can be removed from the sources and the script pattern can simplified to just this,

"scripts": {
  "test": "mocha"
}

please review :)

[iambumblehead]

Planning to merge and publish this soon so changes will be available for the workspace PR #243