Add Docker images to build with crypto backends for Windows, and include cross-builds

Right now, we have -fips tags, but they're limited to building on Linux targeting Linux.

We know that some people do build on Linux targeting Windows. It would help if we provide a tag to do that, rather than forcing them to manually configure GOEXPERIMENT in this particular case.

We also have no FIPS-preconfigured Windows builders, whether targeting Windows or Linux. I don't think we've identified any teams that build this way, but it seems reasonable to fill out the build matrix to have something ready for anyone who does.

We need a new naming scheme for this. I think dropping simple -fips- and mentioning the backend is needed. Simplest is to use the goexperiment string, like:

Something to perhaps point out more directly in our readme is that we don't produce runtime images. These (and the non-FIPS images for that matter) are all meant to be used for builds, not deployment.

• Related: https://github.com/microsoft/go/issues/695
• We could also consider adding e.g. golang:1.21-opensslcrypto-compelfips-bullseye tying in with https://github.com/microsoft/go/issues/928

Start with the existing Docker image definitions and -fips build configuration, then compare the Linux/Windows build and target combinations listed in the issue. Define the backend-aware tag matrix and update the README to state that these are build images, not runtime images; done means the four listed combinations are available.