Use `require('node:buffer')` rather than `Buffer` from global scope

[benmccann]

Node.js recommends importing Buffer from node:buffer:

• https://nodejs.org/api/buffer.html#buffer
• https://nodejs.org/api/buffer.html#nodebuffer-module-apis

Using the Buffer from the global scope is causing issues for some users. E.g. spruceid/siwe#168 and sveltejs/kit#10214 (comment)

[ldthomas]

apg-js version 4.2.0 addresses this issue.