Provide a new Buffer::NewOrCopy method

[Julusian]

Background:

• Electron 21 breaks api compatability with some modules abi-stable-node#441
• node-api: handle no support for external buffers node#45181
• [Bug]: Electron 21 breaks node-api stability guarantees electron/electron#35801

After nodejs/node#45181 it is possible for Buffer::new to fail with napi_no_external_buffers_allowed. A helper method Buffer::NewOrCopy which would try to do a Buffer::new and fallback to doing a Buffer::copy would be helpful and encourage users to code in a way which provides compatibility for both electron and nodejs, without them having to implement the method themselves.

The npm package sharp has implemented this themselves already lovell/sharp@584807b#diff-53a01d31aa585021f8f316c6613dadef86bf1f9ac2070d52daa68adbefbb6ef4.

[mhdawson]

We discussed in the team meeting today, and we agreed it would make sense to add. @legendecas volunteered to put together a PR.

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[legendecas]

Landed in #1273.