Use JS modules as default module mapping

[pepone]

For 3.8 we should consider get rid of our module mapping and go with JS native modules as default.

We should check if it is also possible to get rid of the global used in the browser and just attach the types to the ice module. Currently with browsers each top level module adds a global object

[pepone]

I think we should go one step forward:

• Convert ice package to an ES module
• Generate code always use ES module

Web applications will them use a module bundler, which is already the norm.

[pepone]

Implemented in c353909bfb72cc4ad838939f8f0588aad18e0f1a