Separate node.js and express.js packages

[xr0master]

Problem Statement

@AbhiPrasad In continuation of our conversation, the @sentry/node package has a specific code for express.js. For example https://github.com/getsentry/sentry-javascript/blob/master/packages/node/src/handlers.ts

Solution Brainstorm

Maybe then it should be renamed to @sentry/express, and create a new package for the pure node server.

[HazAT]

We'll consider this when trying to make things easier.