Rework how target platform environments work

[laeubi]

Currently one has to configure target environments rather globally and then they are used to resolve all projects, this currently leads to the situation that each project resolved the same things multiple times. Also if there is a platform filter one still needs to configure one even though the target is known. There is only one place where different environments are relevant and that is for building a product with different natives.

My proposal is to change the behavior so what we already have at some places:

1. If a platform filter is there use that as the target to resolve dependencies
2. Otherwhise use the current running target it it matches any of the configured environments
3. Use all configured ones if it does not match

with the exception of products, but there it should be considered to simply allow to configure additional environments in the materialize-product mojo instead of have them globally.